Yellowfin tuna has a high level of free histidine in their muscle, which can lead to histamine formation by microorganisms if temperature abuse occurs during handling and further processing. The objective of this study was to measure levels of histamine in damaged and undamaged thawed muscle to determine the effect of physical damage on the microbial count and histamine formation during the initial steps of canning processing and to isolate and identify the main histamine-forming microorganisms present in the flesh of yellowfin tuna. Total mesophilic and psicrophilic microorganisms were determined using the standard plate method. The presence of histamine-forming microorganisms was determined in a modified Niven's agar. Strains were further identified using the API 20E kit for enterobacteriaceae and Gram-negative bacilli. Physically damaged tuna did not show higher microbiological contamination than that of undamaged muscle tuna. The most active histamine-forming microorganism present in tuna flesh was Morganella morganii. Other decarboxylating microorganisms present were Enterobacter agglomerans and Enterobacter cloacae. Physical damage of tune during catching and handling did not increase the level of histamine or the amount of microorganisms present in tuna meat during frozen transportation, but they showed a higher risk of histamine-forming microorganism growth during processing.

The use of microbial biofertilizers based on plant-growth-promoting rhizobacteria is a biotechnological alternative to improve production of horticultural crops seedlings. In this study, four bacterial strains previously isolated from tomato (Lycopersicum esculentum Mill.) rhizosphere were identified by using 16S rRNA gene sequence analysis and characterized according to their biochemical properties as plant growth promoters, and their effect on seed germination and seedling growth of tomato and bell pepper (Capsicum annuum L.) was also evaluated. The four strains isolated, named MA04, MA06, MA12 and MA17 and belonging to genus Bacillus, were able to produce indole acetic acid (0.9 to 2.3 mg L-1), to solubilize tricalcium phosphate (18.5 to 34.7 mg L-1), and posess ACC deaminase activity. Furthermore, MA04, MA06 and MA12 can grow in nitrogen free culture medium (with potential atmospheric nitrogen fixing ability). As far as their effect on tomato seeds, MA04 and MA17 improved germination by 5 and 6 % respectively, while MA06 and MA12 strains increased seedling weight by 17 and 20 %, respectively. On pepper seeds, only MA06 increased germination by 7 %, whereas MA12 and MA17 strains increased biomass by 37 and 16 % respectively. The MA12 strain proved to be the most efficient for improving seedling growth of tomato and bell pepper and could be proposed to produce biofertilizers for both plant species.

El empleo de biofertilizantes con base en rizobacterias promotoras del crecimiento, constituye una alternativa biotecnológica para mejorar la producción de especies de interés hortícola. En el presente trabajo se identificaron mediante análisis del gen 16S rRNA, cuatro rizobacterias previamente aisladas de plantas de tomate (Lycopersicum esculentum Mill.), las que fueron caracterizadas por sus propiedades bioquímicas relacionadas con la promoción del crecimiento vegetal y evaluadas por su efecto en la germinación y crecimiento de plántulas de tomate y pimiento (Capsicum annuum L.). Las cuatro cepas, denominadas MA04, MA06, MA12 y MA17, pertenecen al género Bacillus, producen ácido indolacético (0.9 a 2.3 mg L-1), solubilizan fósfato tricálcico (18.5 a 34.7 mg-L-1) y poseen actividad ACC deaminasa. Además, MA04, MA06 y MA12 fueron capaces de crecer en ausencia de nitrógeno (potenciales fijadoras de nitrógeno atmosférico). Al evaluar el efecto de la inoculación de estas rizobacterias en semillas de tomate se encontró que MA04 y MA17 aumentaron el porcentaje de germinación en 5 y 6 % respectivamente, mientras que las cepas MA06 y MA12 incrementaron el peso de las plántulas en 17 y 20 % respectivamente. En semillas de pimiento, la cepa MA06 incrementó el porcentaje de germinación en 7 %, y MA12 y MA17 incrementaron la biomasa en 37 y 16 %, respectivamente. La cepa MA12 fue más versátil para promover el crecimiento de plántulas de tomate y pimiento, y podría recomendarse para la formulación de biofertilizantes destinados al tratamiento de tales cultivos.