Within the European Union (EU), the use of genetically modified organisms (GMOs) in food production is not widely applied and accepted. In contrast to the United States of America, the current EU legislation limits the introduction of functional foods derived from GMOs that may bring a clear benefit to the consumer. Genetically modified lactic acid bacteria (GM-LAB) can be considered as a different class of GMOs, and the European Union is preparing regulations for the risk assessment of genetically modified microorganisms. Since these procedures are not yet implemented, the current risk assessment procedure is shared for GMOs derived from micro organisms, plants, or animals. At present, the use of organisms in food production that have uncontrolled genetic alterations made through random mutagenesis, is permitted, while similar applications with organisms that have controlled genetic alterations are not allowed. The current paper reviews the opportunities that genetically modified lactic acid bacteria may offer the food industry and the consumer. An objective risk profile is described for the use of GM-LAB in food production. To enhance the introduction of functional foods with proven health claims it is proposed to adapt the current safety assessment procedures for (GM)-LAB and suggestions are made for the related cost accountability. A qualified presumption of safety as proposed by SANCO (<a href="#36">EU SANCO 2003</a>), based on taxonomy and on the history of safe use of LAB applied in food, could in the near future be applied to any kind of LAB or GM-LAB provided that a series of modern profiling methods are used to verify the absence of unintended effects of altered LAB that may cause harm to the health of the consumer.

O acetaldeído, responsável pelo sabor e aroma característicos de iogurte, é produzido por diferentes vias metabólicas pelas bactérias lácticas: Streptococcus thermophilus (S. thermophilus) e Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). Neste trabalho, a atenção foi focada especificamente na reação para a formação de acetaldeído e de ácido fólico, catalisada pela enzima serina hidroximetil transferase (SHMT), codificada pelo gene glyA. A enzima SHMT catalisa diversas reações e, no caso da bactéria S. thermophilus, ela exerce também a atividade característica da enzima treonina aldolase (TA), definida como a interconversão do aminoácido treonina em glicina e acetaldeído. Foram construídas linhagens de S. thermophilus (StA2305 e StB2305) com super expressão do gene glyA. Estas linhagens modificadas apresentaram crescimento normal quando o leite foi suplementado com hidrolisado de caseína (Casitione). Quando foram usadas para fermentação de leite, observou-se: aumento na produção de ácido fólico e acetaldeído por StA2305 e aumento significativo na formação de ácido fólico por StB2305.

The typical yogurt flavor is caused by acetaldehyde produced through many different pathways by the yogurt starter bacteria L. bulgaricus and S. thermophilus. The attention was focused on one specific reaction for acetaldehyde and folic acid formation catalyzed by serine hydroxymethyltransferase (SHMT), encoded by the glyA gene. In S. thermophilus, this enzyme SHMT also plays the typical role of the enzyme threonine aldolase (TA) that is the interconvertion of threonine into glycine and acetaldehyde. The behavior of engineered S. thermophilus strains in milk fermentation is described, folic acid and acetaldehyde production were measured and pH and counts were followed. The engineered S. thermophilus strains StA2305 and StB2305, have the glyA gene (encoding the enzyme serine hydroxymethyltransferase) overexpressed. These engineered strains showed normal growth in milk when it was supplemented with Casitione. When they were used in milk fermentation it was observed an increase in folic acid and in acetaldehyde production by StA2305 and for StB2305 it was noticed a significative increase in folic acid formation.