Lactic acid bacteria (LAB) play an important role in the production of fermented food by dairy and wine industries. Decarboxylation of di- and tricarboxylic acids by LAB is a desirable step resulting in the production of compounds that enhance the organoleptic properties and/or the stability of the finished products. However, decarboxylation of amino acids (e.g. histidine, tyrosine) leads to the production of biogenic amines (BA) (e.g. histamine, tyramine), which have undesirable toxic properties. The goal of the present proposal is to acquire an in-depth understanding of the individual acid, and amino acid decarboxylation pathways, to obtain strains unable to produce BA and to generate aroma producer strains resistant to acid stress. We aim to develop strains and systems for the food industries to avoid health risks of BA by controlling their production and, in parallel, to improve the beneficial citrate/malate decarboxylating pathways.
Decarboxylation of metabolites is extremely important for the quality of the fermentation products both in a positive and negative manner, which is dependent on the particular substrate and fermentation process. Metabolism of carboxylic acids generates aroma compounds and lactic acid, which increase organoleptic properties and hygienic quality (impeding growth of pathogenic strains) of the fermentation products, whereas BA production results in food poisoning. The overall objective of the project is to exploit decarboxylation pathways in LAB to develop safe and optimised food technologies. The main goals are:
- to control and/or eliminate the production of BA in fermented food and beverages by utilisation of new LAB strains and/or systems during the fermentation processes. The evaluation and validation of the strains and methods developed in this project will allow the industrial partner to establish a well defined system for the elimination of the health risk associated with the production of BA with the final aim of producing food with safe levels of BA;
- to improve quality of food and beverages by utilisation of new LAB strains, which are acid-resistant and better producers of aroma. The citric and malic acids fermentations result in the production of lactic acid and aroma compounds such as diacetyl, which improve, respectively, the hygienic quality (e.g., impeding the growth of pathogenic strains) and the organoleptic properties of dairy and wine. The validation of the new food-grade LAB strains will allow the industrial partner to obtain bacterial cultures for the production of high quality food and beverages.
The specific objectives of this project are
- to improve screening methods for the detection of LAB producing unwanted BA substances during milk fermentation and wine production;
- to use different LAB as model organisms to develop methods for minimisation of BA production in fermented dairy prducts and wine;
- to develop tools to construct food-grade null mutant alleles and to develop food quality integration systems;
- to construct novel food-grade strains capable of improving and/or modifying the organoleptic properties of dairy products and wine;
- to engineer strains with altered decarboxylating pathways useful for the dairy and wine industries as starter strains;
- to develop new LAB strains resistant to lactate and acidic conditions.
We aim to construct modified strains and to develop systems to minimise the health risk associated with the production of BA in fermented dairy products and wine, and to construct novel strains capable to improve and/or modify the organoleptic properties of cheese and wine.
The specific expected achievements are:
- to develop tools to obtain specific mutant genes,
- to genetically and biochemically characterise the constructed mutant strains, and
- to increase controlled gene expression with the aim of optimising LAB as cell factories with reduced occurrence of hazards.
We will engineer the decarboxylating pathways to reduce the accumulation of poisoning BA, in order to obtain healthful and high quality food products in accordance with one of the most important European society requests. The full exploitation derived from such analyses will be of direct relevance to the competitiveness of biotechnological companies in the European Union.