Antimicrobial potential of pyroligneous extracts – a systematic review and technological prospecting

Juliana Leitzke Santos de Souza Victoria Burmann da Silva Guimarães Angela Diniz Campos Rafael Guerra Lund About the authors

Abstract

Pyroligneous extract is applied in diverse areas as an antioxidant, an antimicrobial, and an anti-inflammatory agent. The discovery of new cost-effective antimicrobial agents of natural origin remains a challenge for the scientific community. This study aimed to conduct a systematic review and a technological forecasting of the existent evidence regarding the use of pyroligneous extract as a potential antimicrobial agent. Studies were identified through an investigation of various electronic databases: PubMed, SciFinder, Web of Science, Scopus, Scielo, Google scholar, and ProQuest. Patents were searched through INPI, Google patents, Espacenet, Patents online, USPTO, and WIPO. The literature on antimicrobial activity of pyroligneous extract are limited given the short duration of studies and variability in study design, use of pyroligneous preparations, and reports on results. However, evidence suggests the potential of pyroligneous extract as a natural antimicrobial agent. The most studied activity was the role of PE as a food preservative. However, pyroligneous extracts are also effective against pathogenic bacteria in the oral microflora and treatment of candidal infections. Further research is needed using standardized preparations of pyroligneous extracts to determine their long-term effectiveness and ability as antimicrobial agents.

Keywords
Food preservation; Antimicrobial; Infections; Preservative; Pharmaceutical

Introduction

Pyroligneous extract (PE), also called pyroligneous acid, liquid smoke, or wood vinegar, is a crude condensate produced from the distillation of smoke generated in wood carbonization. This extract is a complex mixture of compounds derived from the chemical breakdown of wood components through the condensation of vapors and gases generated during the pyrolysis of a limited amount of oxygen.11 Ibrahim D, Kassim J, Lim SH, Rusli W. Evaluation of antibacterial effects of Rhizophora apiculata pyroligneous acid on pathogenic bacteria. Malays J Microbiol. 2014;10(3):197-204. PE is a complex and highly oxygenated aqueous liquid fraction; it results from the thermochemical breakdown or pyrolysis of plant biomass components, such as cellulose, hemicellulose, and lignin.22 Wu Q, Zhang S, Hou B, et al. Study on the preparation of wood vinegar from biomass residues by carbonization process. Bioresour Technol. 2015;179:98-103.,33 Mathew ZA, Zakaria S. Pyroligneous acid—the smoky acidic liquid from plant biomass. Appl Microbiol Biotechnol. 2015;99:11.

PE finds application in diverse areas, acting as an antioxidant, antimicrobial, and anti-inflammatory agent. PE also acts as a source of valuable chemicals and imparts a smoky flavor and antimicrobial protection in food.33 Mathew ZA, Zakaria S. Pyroligneous acid—the smoky acidic liquid from plant biomass. Appl Microbiol Biotechnol. 2015;99:11. PE has been reported to possess extreme antifungal activity against several plant pathogenic fungi44 Oramahi HA, Yoshimura T. Antifungal and antitermitic activities of wood vinegar from Vitex pubescens Vahl. J Wood Sci. 2013;59(4):344-350. and a termiticidal activity.55 Yatagai M. Biological activity of wood vinegar and its recent applications. New Food Ind. 2004;46:5-16. Several researchers have reported the antibacterial activity of PE against several pathogenic bacteria, including plant pathogens.66 Hwang YH, Matsushita YI, Sugamoto K, Matsui T. Antimicrobial effect of the wood vinegar from Cryptomeria japonica sapwood on plant pathogenic microorganisms. J Microbiol Biotechnol. 2005;15(5):1106-1109. Recently, the medicinal use of PE has been studied intensively in the field of oriental medical science, where some natural resources have been used for investigating biological activities.77 Ibrahim D, Kassim J, Sheh-Hong L, Rusli W. Efficacy of pyroligneous acid from Rhizophora apiculata on pathogenic Candida albicans. J Appl Pharm Sci. 2013;3(7):7-13, http://dx.doi.org/10.7324/JAPS.2013.3702.
http://dx.doi.org/10.7324/JAPS.2013.3702...
However, the antimicrobial potential of PE against human and animal pathogenic microorganisms has not been elucidated. Therefore, the present work is carried out to evaluate the antimicrobial potential of PE against human and animal pathogenic microorganisms and organize its present status. PE, a by-product of charcoal-making and often considered as waste, was selected because of its availability in Rio Grande do Sul, Brazil.

Systematic reviews are considered the gold standard for evidence and used to evaluate the benefits and harms of healthcare interventions.88 Pussegoda K, Turner L, Garritty C, et al. Identifying approaches for assessing methodological and reporting quality of systematic reviews: a descriptive study. Syst Rev. 2017;6(1):1-12. Such reviews are much more likely to yield valid conclusions.99 Cook D, Guyatt GH, Laupacis A, Sackett DL, Goldberg RJ. Clinical recommendations using levels of evidence for antithrombotic agents. Chest. 1995;108(4 suppl):227S-230S. The levels of evidence of the studies are ranked according to the degree of confidence, which is related to the methodological quality. Thus, systematic review of the literature occupies the top of the pyramid, followed by randomized clinical trials, cohort studies, case-control, case series, case reports, and lastly, expert opinion and research in animals or in vitro.1010 Cook DJ, Guyatt GH, Ryan G, et al. Should unpublished data be included in meta-analyses? Current convictions and controversies. JAMA. 1993;269(21):2749-2753. This study aimed to search the various electronic databases for articles and online systems of patents and included assays of PE antimicrobial potential for humans and animals.

Material and methods

Eligibility criteria: The inclusion criteria comprised articles and patents that investigated the antimicrobial activity of PE against pathogenic microorganisms of humans and animals.

Information sources and search

This systematic review was conducted according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions,1111 Higgins JPT, Altman DG. In: Higgins JPT, Green S, eds. Cochrane Handbook for Systematic Reviews of Interventions. Version 5.1.0 [Updated March 2011]. The Cochrane Collaboration, 2011. 2011, http://dx.doi.org/10.1002/9780470712184.ch8.
http://dx.doi.org/10.1002/9780470712184....
following the four-phase flow diagram of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement.1212 Moher D, Shamseer L, Clarke M, et al. Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement. Syst Rev. 2015;4(1):1. This report is based on the PRISMA Statement. The following databases were screened: MedLine (PubMed), SciFinder, Web of Science, Scopus, Scielo, Google scholar, and ProQuest. For patents, the sources searched comprised the following: INPI, Google patents, Espacenet, Patents online, USPTO, and WIPO.

The search strategy is described in Table 1, and the focused question is as follows: What is the antimicrobial potential of PE against human and animal pathogenic microorganisms?

Table 1
Search strategy.

Study selection and data collection

Study characteristics, demographic information, enrollment criteria, microorganisms tested, antimicrobial assay types, duration, results, control and groups, and sample size (Tables 2 and 3) were extracted independently for two reviewers (J.L.S.S. and V.B.S.G.). Missing information was sought from authors and/or inventors. The full text papers and patents were assessed independently and in duplicate by the reviewers. Any disagreement on the eligibility of studies included was resolved through discussion and consensus, and in case of disagreement, a third reviewer (R.G.L.) decided whether the article should be included. All titles and abstracts of articles and patents initially found were analyzed and selected in accordance to the eligibility criteria. No restrictions were considered regarding the language and year of publication. The reference lists of studies included were hand-searched for additional articles. Full copies of all potentially relevant studies were identified. Studies that met the inclusion criteria or for which insufficient data were available in the title and abstract to make a decision were selected for full analysis. Authors of the studies were contacted in case of missing data (e.g., data provided in graphs); these studies were only included if the authors provided the missing information. Data extraction was conducted by consensus between the two researchers who conducted the collection.

Table 2
Demographic data from articles and patents considered in this study.
Table 3
Patents data, antibacterial compositions and claims related to pyroligneous extracts antimicrobial activity.

Assessment of risk of bias

The risk of bias for all the included studies was assessed based on The Cochrane Collaboration's tool,1111 Higgins JPT, Altman DG. In: Higgins JPT, Green S, eds. Cochrane Handbook for Systematic Reviews of Interventions. Version 5.1.0 [Updated March 2011]. The Cochrane Collaboration, 2011. 2011, http://dx.doi.org/10.1002/9780470712184.ch8.
http://dx.doi.org/10.1002/9780470712184....
and the methodological quality was adapted from another systematic review of antimicrobial monomers used in dental materials.1313 Cocco AR, De Oliveira Da Rosa WL, Da Silva AF, Lund RG, Piva E. A systematic review about antibacterial monomers used in dental adhesive systems: current status and further prospects. Dent Mater. 2015;31(11):1345-1362. The parameters used for the evaluation of methodology assays were discussed by the researchers involved, and judgment was carried out by group discussion. Assessment of risk of bias was conducted using Review Manager 5.3 software.

Results

Results of searches

After database screening [Pubmed (16), Scopus (8), SciFinder (27), Web of Science (9), Scielo (0), Google scholar (34), and ProQuest (3)] and removal of duplicates, 89 studies were identified. After title and abstract screening, 29 studies remained, and this number was reduced to 14 after careful examination of the full texts. The last electronic search was conducted on December 4th, 2017. Fig. 1 shows a flowchart summarizing the selection process of articles and patents.

Fig. 1
Flow chart.

Of the 89 articles initially recovered from all databases, 75 articles were excluded because they were not related to the antimicrobial activity of PE and failed to satisfy the selection criteria. A total of 60 articles were excluded after reading the title and abstract, and 12 were excluded after screening the full text because they tested properties other than antimicrobial pathology for humans or animals. One study tested an intestinal protozoan parasite that causes diarrhea in both humans and domestic animals1414 Watarai S, Koiwa M. Feeding activated charcoal from bark containing wood vinegar liquid (nekka-rich) is effective as treatment for cryptosporidiosis in calves. J Dairy Sci. 2008;91(4):1458-1463.; one article used an agent accelerating the growth of plants and the development of roots.1515 Zhai M, Shi G, Wang Y, et al. Functionality of liquid smoke as an all-natural antimicrobial in food preservation. Bioresour Technol. 2010;10(1):6219-6224. PE has been studied as a repellent and insecticide against insect pests to crops,55 Yatagai M. Biological activity of wood vinegar and its recent applications. New Food Ind. 2004;46:5-16. as an antimicrobial agent for wood fungi, and as a weed control agent.44 Oramahi HA, Yoshimura T. Antifungal and antitermitic activities of wood vinegar from Vitex pubescens Vahl. J Wood Sci. 2013;59(4):344-350.,66 Hwang YH, Matsushita YI, Sugamoto K, Matsui T. Antimicrobial effect of the wood vinegar from Cryptomeria japonica sapwood on plant pathogenic microorganisms. J Microbiol Biotechnol. 2005;15(5):1106-1109.,1616 Lee SH, H’ng PS, Lee AN, Sajap AS, Tey BT, Salmiah U. Production of pyroligneous acid from lignocellulosic biomass and their effectiveness against biological attacks. J Appl Sci. 2010;10(20):2440-2446.1919 Wei Q, Ma X, Dong J. Preparation, chemical constituents and antimicrobial activity of pyroligneous acids from walnut tree branches. J Anal Appl Pyrolysis. 2010;87(1):24-28. Two studies used the PE as phenol source and tested the antibacterial activity of separate components.2020 Lebois M, Connil N, Onno B, Prévost H, Dousset X. Effects of divercin V41 combined to NaCl content, phenol (liquid smoke) concentration and pH on Listeria monocytogenes ScottA growth in BHI broth by an experimental design approach. J Appl Microbiol. 2004;96(5):931-937.,2121 Thurette J, Membre JM, Ching LH, Tailiez R, Catteau M. Behavior of Listeria spp. in smoked fish products affected by liquid smoke, NaCl concentration, and temperature. J Food Prot. 1998;61(11):1475-1479. In addition, two articles were excluded as the researchers featured no access to full text versions,2222 Wang H, Cao H. Progress of antimicrobial mechanism of wood vinegar from agricultural and forestry wastes. J Agro-Environ. 2014;42:741-742.,2323 Qin W, XiHan M, Tao Z. Preparation, chemical constituents analysis and antimicrobial activities of pyroligneous acid of walnut shell. Trans Chinese Soc Agric Eng. 2008;24(7):276-279. and one article was a review study.2424 Lingbeck J, Cordero P, O’Bryan CA, Johnson MG, Ricke SC, Crandall PG. Functionality of liquid smoke as an all-natural antimicrobial in food preservation. Meat Sci. 2014;97(2):197-206.

In the patent databases, INPI (0), Google patents (0), Espacenet (7), patents on line (44), USPTO (11), and WIPO (7), the search strategy initially retrieved 69 patents. After removal of duplicates, this number was reduced to 37. A total of 25 patents were excluded after reading the titles and abstracts (Fig. 1) as they were not related to PE. Of the remaining 12 patents, 1 patent was excluded because it reported a promoter of environmental properties in soil, plants, and fish.2525 Wada S. Promoter for sound activation of natural environment and its production. Espac JP19900418589 – Japan. 1994, 656617(19940301). https://worldwide.espacenet.com/publicationDetails/biblio?II=2&ND=3&adjacent=true&locale=en_EP&FT=D&date=19940301&CC=JP&NR=H0656617A&….
https://worldwide.espacenet.com/publicat...
Twelve patents were included in the analysis.

Study characteristics

Table 2 describes the microorganisms tested, the source of PE, concentrations, methodologies used and the application area for each study from articles, and patents selected in the search. Table 3 shows the data of the patents included in this review.

All articles were published between 1998 and 2014. Most studies showed different cellulose sources to burn and generate different types of PE for its test as an antimicrobial agent. Several sources were commercial extracts,11 Ibrahim D, Kassim J, Lim SH, Rusli W. Evaluation of antibacterial effects of Rhizophora apiculata pyroligneous acid on pathogenic bacteria. Malays J Microbiol. 2014;10(3):197-204.,77 Ibrahim D, Kassim J, Sheh-Hong L, Rusli W. Efficacy of pyroligneous acid from Rhizophora apiculata on pathogenic Candida albicans. J Appl Pharm Sci. 2013;3(7):7-13, http://dx.doi.org/10.7324/JAPS.2013.3702.
http://dx.doi.org/10.7324/JAPS.2013.3702...
,2626 Harada K, Iguchi A, Yamada M, Hasegawa K, Nakata T, Hikasa Y. Determination of maximum inhibitory dilutions of bamboo pyroligneous acid against pathogenic bacteria from companion animals: an in vitro study. J Vet Adv. 2013;3(11):300-305.3333 Lingbeck J, Cordero P, O’Bryan CA, Johnson MG, Ricke SC, Crandall PG. Temperature effects on the antimicrobial efficacy of condensed smoke and lauric arginate against Listeria and Salmonella. J Food Prot. 2014;77(6):934-940. and others were experimental extracts.1919 Wei Q, Ma X, Dong J. Preparation, chemical constituents and antimicrobial activity of pyroligneous acids from walnut tree branches. J Anal Appl Pyrolysis. 2010;87(1):24-28.,3434 Gao H, Su Y, Zhang Q, et al. Chemical constituents analysis and antimicrobial activities of pyroligneous acid of Eucommia ulmoides Oliv. Branch. Acta Bot Boreal-Occídent Sin 2011. 2011;31(10):2106-2112, 1000-4025(2011)10-2106-07 精J.,3535 Kim SP, Kang MY, Park JC, Nam SH, Friedman M. Rice hull smoke extract inactivates Salmonella Typhimurium in laboratory media and protects infected mice against mortality. J Food Sci. 2012;77(1):80-85. One study tested microbial strains isolated from dogs and cats.2626 Harada K, Iguchi A, Yamada M, Hasegawa K, Nakata T, Hikasa Y. Determination of maximum inhibitory dilutions of bamboo pyroligneous acid against pathogenic bacteria from companion animals: an in vitro study. J Vet Adv. 2013;3(11):300-305. One article analyzed four strains of pathogenic Candida albicans, which were isolated from patients suffering from urinary tract infection (two strains), vaginitis, and onychomycosis (one each),77 Ibrahim D, Kassim J, Sheh-Hong L, Rusli W. Efficacy of pyroligneous acid from Rhizophora apiculata on pathogenic Candida albicans. J Appl Pharm Sci. 2013;3(7):7-13, http://dx.doi.org/10.7324/JAPS.2013.3702.
http://dx.doi.org/10.7324/JAPS.2013.3702...
and one tested another C. albicans strain.3030 Suñen E. Minimum inhibitory concentrations of smoke wood extracts against spoilage and pathogenic micro-organisms associated with foods. Lett Appl Microbiol. 1998;27:45-48. One study tested PE as an agent to prevent viral epidemics in agricultural and human environments.2727 Marumoto S, Yamamoto SP, Nishimura H, et al. Identification of a germicidal compound against picornavirus in bamboo pyroligneous acid. J Agric Food Chem. 2012;60(36):9106-9111. Various studies reported PE as a food preservative.2828 Milly PJ, Toledo RT, Chen J. Evaluation of liquid smoke treated ready-to-eat (RTE) meat products for control of Listeria innocua M1. J Food Sci. 2008;73(4):M179-M183.,3030 Suñen E. Minimum inhibitory concentrations of smoke wood extracts against spoilage and pathogenic micro-organisms associated with foods. Lett Appl Microbiol. 1998;27:45-48.,3131 Suñen E, Fernandez-Galian B, Aristimuño C. Antibacterial activity of smoke wood condensates against Aeromonas hydrophila, Yersinia enterocolitica and Listeria monocytogenes at low temperature. Food Microbiol. 2001;18(4):387-393.,3333 Lingbeck J, Cordero P, O’Bryan CA, Johnson MG, Ricke SC, Crandall PG. Temperature effects on the antimicrobial efficacy of condensed smoke and lauric arginate against Listeria and Salmonella. J Food Prot. 2014;77(6):934-940.,3636 Van Loo EJ, Babu D, Crandall PG, Ricke SC, Van LE. Screening of commercial and pecan shell-extracted liquid smoke agents as natural antimicrobials against foodborne pathogens. J Food Prot. 2012;75(6):1148-1152.,3737 Kim SP, Yang YJ, Kang MY, et al. Composition of liquid rice hull smoke and anti-inflammatory effects in mice. J Agric Food Chem. 2011;59:4570-4581. Only one in vivo study used Salmonella-infected Balb/c mouse model.3535 Kim SP, Kang MY, Park JC, Nam SH, Friedman M. Rice hull smoke extract inactivates Salmonella Typhimurium in laboratory media and protects infected mice against mortality. J Food Sci. 2012;77(1):80-85. All in vitro studies reported the bacterial or antifungal activity of PE. The methods used for the tests included disk diffusion and minimum inhibitory concentration. The growth profile of the bacteria was examined via time-kill and viral inactivation assays.2727 Marumoto S, Yamamoto SP, Nishimura H, et al. Identification of a germicidal compound against picornavirus in bamboo pyroligneous acid. J Agric Food Chem. 2012;60(36):9106-9111.

Regarding patent documents, the data showed 11 patents deposited from 1981 to 2009. Antibacterial, antifungal, and preservative proprieties of PE were found in these patents, which claimed PE incorporation into additives for the treatment of animal feedstuffs,3838 Tribble TB, Rose GW. Antimicrobial treatment and preservation of animal feedstuffs. United States Pat 4308293. 1981:1–9 http://www.freepatentsonline.com/4308293.html.
http://www.freepatentsonline.com/4308293...
fiber-reinforced cellulosic food casing,3939 Chiu HS. Liquid smoke impregnated fibrous food casing. United States Pat 4377187. 1983:1–20 http://www.freepatentsonline.com/4377187.html.
http://www.freepatentsonline.com/4377187...
compositions for food preservation,4040 Bakal GJ. Preservatives for food. United States Pat Appl 20090011096. 2008:1–6 http://www.freepatentsonline.com/y2009/0011096.html.
http://www.freepatentsonline.com/y2009/0...
4242 Patrick W, Ramakrishnam sreekumar F. Natural biodeodorizing agent composition. US 536160. 2004;1(19):1-43. carbon fiber,4343 Matsui S. Production of carbon fiber and carbon fiber produced thereby. Espac JP19980339429 – Japan. 1998;2000160476(2000160476), 20000613. https://worldwide.espacenet.com/publicationDetails/biblio?II=1&ND=3&adjacent=true&locale=en_EP&FT=D&date=20000613&CC=JP&NR=2000160476A&….
https://worldwide.espacenet.com/publicat...
cosmetic composition,4444 Chang MS. Cosmetic composition containing pyroligneous acid solution. Espac KR20030005075 A - Korea. 2003;2003000507(20030005075), 20030115. https://worldwide.espacenet.com/publicationDetails/biblio?II=0&ND=3&adjacent=true&locale=en_EP&FT=D&date=20030115&CC=KR&NR=20030005075A….
https://worldwide.espacenet.com/publicat...
biodeodorizing agent,4545 Ko SH, Lee HS, Park GS, Park SJ, Sim DS, Song HJ. Natural biodeodorizing agent composition. Espac KR20010048390. 2003;2003001405(20030014052), 20030215. https://worldwide.espacenet.com/publicationDetails/biblio?II=1&ND=3&adjacent=true&locale=en_EP&FT=D&date=20030215&CC=KR&NR=20030014052A….
https://worldwide.espacenet.com/publicat...
antimicrobial compositions,4646 Lee JH, Bai DG, Cho KJ, Huh SM, Park SH. Silver-ionized wood vinegar having enhanced antimicrobial activity and use thereof for improving or preventing disease caused by pathogenic bacteria. Espac KR20060109757 A - Korea. 2005;2006010975(20060109757). https://worldwide.espacenet.com/publicationDetails/biblio?II=0&ND=3&adjacent=true&locale=en_EP&FT=D&date=20061023&CC=KR&NR=20060109757A….
https://worldwide.espacenet.com/publicat...
pharmaceutical composition for symptoms of atopic dermatitis,4747 Byun MW. Pharmaceutical composition for ameliorating symptoms of atopic dermatitis without skin irritation comprising refined nontoxic wood vinegar having no harmful materials. PATENTSCOPE KR1020070042868 - Korea. 2007:970334. https://patentscope.wipo.int/search/en/detail.jsf?docId=KR970334&recNum=1&office=&queryString=FP%3A%28wood+vinegar+AND+antimicrobial+activ…
https://patentscope.wipo.int/search/en/d...
and compositions for oral microbes.4848 Wu Y, Bedford J, Riley K. Antimicrobial smoke flavor for oral microflora control United. United States Pat Appl 20070212310. 2007:2013-2014, http://dx.doi.org/10.1177/001440299105800203.
http://dx.doi.org/10.1177/00144029910580...

Discussion

From the literature reviewed, most researchers have reported promising results for PE as an antimicrobial agent. The most studied activity for PE was for food preservative, with seven articles2828 Milly PJ, Toledo RT, Chen J. Evaluation of liquid smoke treated ready-to-eat (RTE) meat products for control of Listeria innocua M1. J Food Sci. 2008;73(4):M179-M183.3333 Lingbeck J, Cordero P, O’Bryan CA, Johnson MG, Ricke SC, Crandall PG. Temperature effects on the antimicrobial efficacy of condensed smoke and lauric arginate against Listeria and Salmonella. J Food Prot. 2014;77(6):934-940. and five patents presenting related results.3838 Tribble TB, Rose GW. Antimicrobial treatment and preservation of animal feedstuffs. United States Pat 4308293. 1981:1–9 http://www.freepatentsonline.com/4308293.html.
http://www.freepatentsonline.com/4308293...
,3939 Chiu HS. Liquid smoke impregnated fibrous food casing. United States Pat 4377187. 1983:1–20 http://www.freepatentsonline.com/4377187.html.
http://www.freepatentsonline.com/4377187...
,4141 Lindner RL. Meat processing with Listeria monocytogene re-inoculation control stage. United States Pat 5043174. 1991:1–6 http://www.freepatentsonline.com/5043174.html.
http://www.freepatentsonline.com/5043174...
,4242 Patrick W, Ramakrishnam sreekumar F. Natural biodeodorizing agent composition. US 536160. 2004;1(19):1-43.,4848 Wu Y, Bedford J, Riley K. Antimicrobial smoke flavor for oral microflora control United. United States Pat Appl 20070212310. 2007:2013-2014, http://dx.doi.org/10.1177/001440299105800203.
http://dx.doi.org/10.1177/00144029910580...
The PE was effective for the following microorganisms important for the food industry: Salmonella enteritidis, Salmonella typhimurium, Salmonella muenster, Salmonella seftenburg, Escherichia coli, Staphylococcus aureus, Pseudomonas putida, Pseudomonas aeruginosa, Lactobacillus plantarum, Listeria innocua, Listeria monocytogenes, Aeromonas hydrophila, Yersinia enterocolitica, Saccharomyces cerevisiae, and Aspergillus niger. Table 2 shows all the strains tested in each study. PE was used as antimicrobial in food preservation and has demonstrated abilities to reduce or inhibit pathogenic and spoilage organisms. Comparing results of studies presented difficulty given their various differences. These studies used different methodologies for the antimicrobial activity and for preparation of PE. Some studies provided no information on the preparations. Most commercial extracts were tested for use as food preservative; one was for viral epidemics, two for antibacterial activity, and another for antifungal infections.

Suñen et al. (1998) tested seven commercial preparations of PE used in food industry in Spain against L. monocytogenes and other pathogenic microorganisms.3030 Suñen E. Minimum inhibitory concentrations of smoke wood extracts against spoilage and pathogenic micro-organisms associated with foods. Lett Appl Microbiol. 1998;27:45-48. In 2001, the same author tested four other commercial preparations of PE used in the Spanish food industry and evaluated their antimicrobial properties at low temperature against A. hydrophila, Y. enterocolitica, and L. monocytogenes. All four extracts effectively eliminated or suppressed the growth of A. hydrophila after 21 days.3131 Suñen E, Fernandez-Galian B, Aristimuño C. Antibacterial activity of smoke wood condensates against Aeromonas hydrophila, Yersinia enterocolitica and Listeria monocytogenes at low temperature. Food Microbiol. 2001;18(4):387-393. Another study on food preservative examined the effects of selected PEs on the control of L. monocytogenes in frankfurters. Treatments with PE reduced and controlled L. monocytogenes growth in the most permissive franks for 10 weeks.3232 Gedela S, Escoubas JR, Muriana PM. Effect of inhibitory liquid smoke fractions on Listeria monocytogenes during long-term storage of frankfurters. J Food Prot. 2007;70(2):386-391. Milly et al. (2008) used PE fractions applied on ready-to-eat meat products to control the growth of inoculated L. innocua M1.2828 Milly PJ, Toledo RT, Chen J. Evaluation of liquid smoke treated ready-to-eat (RTE) meat products for control of Listeria innocua M1. J Food Sci. 2008;73(4):M179-M183.

In 2012, Van Loo et al. investigated the antibacterial activity of eight commercial PE samples against S. enteritidis, S. aureus, and E. coli, demonstrating that the commercial smokes inhibited the growth of these foodborne pathogens.3636 Van Loo EJ, Babu D, Crandall PG, Ricke SC, Van LE. Screening of commercial and pecan shell-extracted liquid smoke agents as natural antimicrobials against foodborne pathogens. J Food Prot. 2012;75(6):1148-1152.

Harada et al. (2013) determined the maximum inhibitory dilutions of bamboo PE against 104 E. coli, 112 Staphylococcus pseudintermedius, and 58 P. aeruginosa strains isolated from dogs and cats. The results indicated that bamboo pyroligneous acid exerts significantly inhibit the growth of representative bacterial pathogens from companion animals, although inhibition differed among species.2626 Harada K, Iguchi A, Yamada M, Hasegawa K, Nakata T, Hikasa Y. Determination of maximum inhibitory dilutions of bamboo pyroligneous acid against pathogenic bacteria from companion animals: an in vitro study. J Vet Adv. 2013;3(11):300-305.

Bamboo PE-inactivated picornavirus and encephalomyocarditis virus showed that phenol is the sole germicidal component, and that acetic acid augmented the phenol inactivating activity. These findings suggest that bamboo PE is a potentially useful agent to prevent viral epidemics in agricultural and human environments.2727 Marumoto S, Yamamoto SP, Nishimura H, et al. Identification of a germicidal compound against picornavirus in bamboo pyroligneous acid. J Agric Food Chem. 2012;60(36):9106-9111.

Ibrahim et al. (2013) tested the PE, concentrated PE, and dichloromethane extracts of CPA, namely, DCM A and B, against four pathogenic strains of C. albicans. The results exhibited significant inhibition zones. The results also revealed that extract DCM B of CPA showed the most significant potential as an anti-candidal agent.77 Ibrahim D, Kassim J, Sheh-Hong L, Rusli W. Efficacy of pyroligneous acid from Rhizophora apiculata on pathogenic Candida albicans. J Appl Pharm Sci. 2013;3(7):7-13, http://dx.doi.org/10.7324/JAPS.2013.3702.
http://dx.doi.org/10.7324/JAPS.2013.3702...
In 2014, the author concluded that Rhizophora apiculata PE may also be a broad antimicrobial agent against pathogenic bacteria.4949 Ibrahim D, Kassim J, Lim S, Rusli W. Evaluation of antibacterial effects of Rhizophora apiculata pyroligneous acid on pathogenic bacteria. Malaysian J Microbiol. 2014;10(3):197-204.

Other authors investigated the effects of temperature on antimicrobial properties of two commercial PE fractions and PE derived from pecan shells, against two common foodborne pathogens, Listeria and Salmonella. Understanding how storage temperature affects the efficacy of antimicrobials is an important factor that can contribute to reducing high levels and costs of antimicrobials and ultimately improve food safety for consumers.3333 Lingbeck J, Cordero P, O’Bryan CA, Johnson MG, Ricke SC, Crandall PG. Temperature effects on the antimicrobial efficacy of condensed smoke and lauric arginate against Listeria and Salmonella. J Food Prot. 2014;77(6):934-940.

Three papers reported the development of new experimental PE. They tested different kinds of cellulose as feedstock: walnut tree branches, Eucommia ulmoides, olive branch, and rice hull. Wei et al. (2010) prepared and collected PE by pyrolizing walnut tree branches at three temperature ranges: 90 °C–230 °C, 230 °C–370 °C, and 370 °C–450 °C. All the PEs exhibited antibacterial activity. The high level of antibacterial activity of WP3 indicated that pyroligneous acids collected at higher temperature feature stronger inhibition effects on bacteria.1919 Wei Q, Ma X, Dong J. Preparation, chemical constituents and antimicrobial activity of pyroligneous acids from walnut tree branches. J Anal Appl Pyrolysis. 2010;87(1):24-28.

PE of E. ulmoides olive branch was collected at different temperature ranges: 90 °C–200 °C, 200 °C–340 °C, and 340 °C–520 °C. The results showed that the maximum amount of the PE was collected at the range 200 °C–340 °C and also showed the most anti-pathogenic activities. After the preliminary analysis, phenols were considered the active components of bacteriostatic activity.3434 Gao H, Su Y, Zhang Q, et al. Chemical constituents analysis and antimicrobial activities of pyroligneous acid of Eucommia ulmoides Oliv. Branch. Acta Bot Boreal-Occídent Sin 2011. 2011;31(10):2106-2112, 1000-4025(2011)10-2106-07 精J.

A previously characterized rice hull PE was tested for bactericidal activity against S. typhimurium using the disk-diffusion method. The in vivo antibacterial activity of rice hull smoke extract (1.0%, v/v) was also examined in a Salmonella-infected Balb/c mouse model. The combination of rice hull smoke extract and vancomycin acted synergistically against the pathogen. The beneficial results suggest that the rice hull PE possesses the potential to complement wood-derived smokes as antimicrobial flavor formulation for application in human foods and animal feeds.3535 Kim SP, Kang MY, Park JC, Nam SH, Friedman M. Rice hull smoke extract inactivates Salmonella Typhimurium in laboratory media and protects infected mice against mortality. J Food Sci. 2012;77(1):80-85.

Technology prospecting for PE as an antimicrobial agent: the patent search

Studies on PE in patents were older than articles. In 1981, PEs incorporating selective additives were used as antifungal and antibacterial preservative agents for the treatment of animal feedstuffs.3838 Tribble TB, Rose GW. Antimicrobial treatment and preservation of animal feedstuffs. United States Pat 4308293. 1981:1–9 http://www.freepatentsonline.com/4308293.html.
http://www.freepatentsonline.com/4308293...
In 1983, PE was used in a fibrous reinforced cellulosic food casing with PE to provide antimycotic quality in the casing without separating antimycotic agent.3939 Chiu HS. Liquid smoke impregnated fibrous food casing. United States Pat 4377187. 1983:1–20 http://www.freepatentsonline.com/4377187.html.
http://www.freepatentsonline.com/4377187...
In 1991, a PE derivative product was applied to wieners post-peeling and before packaging to inhibit L. monocytogenes reinoculation and extend the shelf life of the wieners without adversely affecting their taste and/or edibility.4141 Lindner RL. Meat processing with Listeria monocytogene re-inoculation control stage. United States Pat 5043174. 1991:1–6 http://www.freepatentsonline.com/5043174.html.
http://www.freepatentsonline.com/5043174...
In 2004 and 2008, other patents developed methods and compositions for antimicrobial treatment of food products.4040 Bakal GJ. Preservatives for food. United States Pat Appl 20090011096. 2008:1–6 http://www.freepatentsonline.com/y2009/0011096.html.
http://www.freepatentsonline.com/y2009/0...
,4242 Patrick W, Ramakrishnam sreekumar F. Natural biodeodorizing agent composition. US 536160. 2004;1(19):1-43.

The antimicrobial property of PE was used for the development of carbon fiber by soaking carbon fibers in a heat treatment solution mainly comprising PE from wood or bamboo.4343 Matsui S. Production of carbon fiber and carbon fiber produced thereby. Espac JP19980339429 – Japan. 1998;2000160476(2000160476), 20000613. https://worldwide.espacenet.com/publicationDetails/biblio?II=1&ND=3&adjacent=true&locale=en_EP&FT=D&date=20000613&CC=JP&NR=2000160476A&….
https://worldwide.espacenet.com/publicat...
PE was also used as biodeodorizing agent composition containing a culture solution; the PE solution showed an excellent antimicrobial activity against putrefactive or pathogenic bacteria and a long-lasting deodorizing effect.4545 Ko SH, Lee HS, Park GS, Park SJ, Sim DS, Song HJ. Natural biodeodorizing agent composition. Espac KR20010048390. 2003;2003001405(20030014052), 20030215. https://worldwide.espacenet.com/publicationDetails/biblio?II=1&ND=3&adjacent=true&locale=en_EP&FT=D&date=20030215&CC=KR&NR=20030014052A….
https://worldwide.espacenet.com/publicat...

Two studies developed antimicrobial products for skin; a cosmetic composition containing a PE solution featuring an antimicrobial activity and antioxidant activity as a main component was obtained and considered suitable for skin protection.4444 Chang MS. Cosmetic composition containing pyroligneous acid solution. Espac KR20030005075 A - Korea. 2003;2003000507(20030005075), 20030115. https://worldwide.espacenet.com/publicationDetails/biblio?II=0&ND=3&adjacent=true&locale=en_EP&FT=D&date=20030115&CC=KR&NR=20030005075A….
https://worldwide.espacenet.com/publicat...
A pharmaceutical composition for ameliorating symptoms of atopic dermatitis comprising refined PE was proven to avoid side effects, such as skin irritation and bad smell, by removing harmful materials and toxicity and improving antimicrobial activity.4747 Byun MW. Pharmaceutical composition for ameliorating symptoms of atopic dermatitis without skin irritation comprising refined nontoxic wood vinegar having no harmful materials. PATENTSCOPE KR1020070042868 - Korea. 2007:970334. https://patentscope.wipo.int/search/en/detail.jsf?docId=KR970334&recNum=1&office=&queryString=FP%3A%28wood+vinegar+AND+antimicrobial+activ…
https://patentscope.wipo.int/search/en/d...

One patent developed a silver-ionized PE to enhance antimicrobial activity of PE against pathogenic bacteria: E. coli, Salmonella sp., Bacillus sp., Staphylococcus sp., Vibrio sp., Aspergillus sp., Fusarium sp., Tricoderma sp., and Candida sp.4646 Lee JH, Bai DG, Cho KJ, Huh SM, Park SH. Silver-ionized wood vinegar having enhanced antimicrobial activity and use thereof for improving or preventing disease caused by pathogenic bacteria. Espac KR20060109757 A - Korea. 2005;2006010975(20060109757). https://worldwide.espacenet.com/publicationDetails/biblio?II=0&ND=3&adjacent=true&locale=en_EP&FT=D&date=20061023&CC=KR&NR=20060109757A….
https://worldwide.espacenet.com/publicat...
Another patent used PE against pathogenic microorganisms of oral cavity and provided compositions and methods to inhibit the growth of oral microbes and promote oral care.4848 Wu Y, Bedford J, Riley K. Antimicrobial smoke flavor for oral microflora control United. United States Pat Appl 20070212310. 2007:2013-2014, http://dx.doi.org/10.1177/001440299105800203.
http://dx.doi.org/10.1177/00144029910580...

The examination of PE as an antimicrobial agent, the broad spectrum of its properties, with and without enhancing additives, was evaluated against heat-resistant, spore-forming, aerobic bacilli, gram-negative bacillus associated with avian, and human enteritis. Various saprophytic molds (mycelial fungi) are associated with animal feeds, spoilage and, in several instances, human and animal mycotoxicoses. In each instance, our findings indicate that PE effectively and irreversibly reduces natural and/or experimental microbial contaminants associated to animal feedstuffs.3838 Tribble TB, Rose GW. Antimicrobial treatment and preservation of animal feedstuffs. United States Pat 4308293. 1981:1–9 http://www.freepatentsonline.com/4308293.html.
http://www.freepatentsonline.com/4308293...

Cellulosic sources of PE

The cellulose sources reported in the studies included in this systematic review comprised woods of hickory, mesquite, apple, pecan, moso bamboo (Phyllostachys pubescens), Rhizophora apiculata, walnut tree branches, and E. ulmoides olive. Branch and rice hull and five studies presented no information about these cellulose sources.

Future prospects for PE

Further in vivo studies are required for the development of new products using PE and the investigation of its possible use as an antimicrobial agent against resistant pathogenic microorganisms and development of pharmaceutical medicines. Many pathogenic microorganisms are tested for use as food preservative; this extract demonstrated a remarkable antimicrobial potential but was not identified in in vivo studies for humans or clinical assays.

Conclusion

In conclusion, the evidence suggests that PE features an antimicrobial activity against pathogenic microorganisms for humans and animals. Its use is prolonged and safe in food products. However, only one study was conducted on animals, and no clinical case was found.

  • Funding sources
    The authors would like to thank the Brazilian research support agencies CAPES and FAPERGS for the financial support (PqG – Grant #17/2551-0001067-1).

Acknowledgments

The authors wish to thank the Coordination for the Improvement of Higher Education Personal (CAPES, Brazil) for the granting of Doctorate's scholarship for the first author.

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Publication Dates

  • Publication in this collection
    Nov 2018

History

  • Received
    28 Feb 2018
  • Accepted
    1 July 2018
  • Published
    14 Aug 2018
Sociedade Brasileira de Microbiologia USP - ICB III - Dep. de Microbiologia, Sociedade Brasileira de Microbiologia, Av. Prof. Lineu Prestes, 2415, Cidade Universitária, 05508-900 São Paulo, SP - Brasil, Ramal USP 7979, Tel. / Fax: (55 11) 3813-9647 ou 3037-7095 - São Paulo - SP - Brazil
E-mail: bjm@sbmicrobiologia.org.br