Strategies for improvement of gamma-aminobutyric acid (GABA) biosynthesis via lactic acid bacteria (LAB) fermentation.

Gamma-aminobutyric acid (GABA) is a non-protein amino acid widely distributed in nature and extensively explored for its numerous physiological functions and effects on metabolic disorders. Lactic acid bacteria (LAB) are one of the most important GABA producers, vigorously pursued due to their high GABA content and generally regarded as safe (GRAS) status that allows for direct formulation in various GABA-enriched food products. To meet the strict requirements of the food and nutraceutical industries, the biosynthesis of GABA is typically preferred over the chemical synthesis route. The production of GABA varies among various strains of LAB and is affected by different fermentation conditions. Hence, optimizing the fermentation conditions to enhance the activity of the key enzyme glutamic acid decarboxylase is essential to maximize GABA production. This paper reviews the beneficial effects of GABA on human health and its applications in fermented food products. A particular emphasis is given to the biosynthetic approach for producing GABA by various LAB species via the microbial fermentation route. Efficient strategies for enhancing GABA production through optimization of the fermentation conditions, mode of fermentation, two-step fermentation, co-culturing approach, immobilization technique and genetic engineering are discussed in detail.

Enhancement of Biomass and Calcium Carbonate Biomineralization of Chlorella vulgaris through Plackett-Burman Screening and Box-Behnken Optimization Approach.

The biosynthesis of calcium carbonate (CaCO3) minerals through a metabolic process known as microbially induced calcium carbonate precipitation (MICP) between diverse microorganisms, and organic/inorganic compounds within their immediate microenvironment, gives rise to a cementitious biomaterial that may emerge as a promissory alternative to conventional cement. Among photosynthetic microalgae, Chlorella vulgaris has been identified as one of the species capable of undergoing such activity in nature. In this study, response surface technique was employed to ascertain the optimum condition for the enhancement of biomass and CaCO3 precipitation of C. vulgaris when cultured in Blue-Green (BG)-11 aquaculture medium. Preliminary screening via Plackett-Burman Design showed that sodium nitrate (NaNO3), sodium acetate, and urea have a significant effect on both target responses (p < 0.05). Further refinement was conducted using Box-Behnken Design based on these three factors. The highest production of 1.517 g/L C. vulgaris biomass and 1.143 g/L of CaCO3 precipitates was achieved with a final recipe comprising of 8.74 mM of NaNO3, 61.40 mM of sodium acetate and 0.143 g/L of urea, respectively. Moreover, polymorphism analyses on the collected minerals through morphological examination via scanning electron microscopy and crystallographic elucidation by X-ray diffraction indicated to predominantly calcite crystalline structure.

Novel approaches to purifying bacteriocin: A review.

Bacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted.