The Use of γ-Aminobutyric Acid-Producing Saccharomyces cerevisiae SC125 for Functional Fermented Beverage Production from Apple Juice

Stress-Driven Production of γ-Aminobutyric Acid Using Non-Conventional Yeast Strains Kluyveromyces marxianus JMY140K and Metschnikowia reukaufii JMY075

γ-Aminobutyric acid (GABA) is a valuable amino acid widely used in food, healthcare, and agriculture. GABA bioproduction by budding yeasts has been commonly reported, but related studies using non-conventional yeasts remain limited. In this study, two non-conventional natural yeast strains, namely, Kluyveromyces marxianus JMY140K and Metschnikowia reukaufii JMY075, were identified as promising GABA producers, and M. reukaufii JMY075 was discovered to be a GABA producer. Enhanced GABA production was observed in the two yeast strains under stress conditions, including high temperature and high ethanol and acetic acid levels. In particular, K. marxianus JMY140K showed 7.93 times higher GABA titers under thermal stress than that of the control. External stress conditions significantly influenced the GABA production of these two yeast strains. The culture filtrate of K. marxianus JMY140K also showed promising activities in human skin cells. In addition, K. marxianus JMY140K could also produce GABA using rice straw hydrolysate, which indicated that it has the potential to produce GABA using renewable biomass. Our studies provide insight for further enhancing the GABA production of natural yeasts and promoting its biotechnology applications.

Widely targeted metabolomics and flavoromics reveal the effect of Wickerhamomyces anomalus fermentation on the volatile and nonvolatile metabolites of black garlic juice

Black garlic has a variety of biological activities, but many consumers cannot accept it because of the garlic odor and the bitter taste. In this study, fermentation with yeast Wickerhamomyces anomalus was adopted to improve the flavor of black garlic juice. Although fermentation reduced antioxidant activities, the garlicky odor and bitter taste were weakened. Metabolomic analysis revealed 141 metabolites were significantly differentially regulated. The upregulated metabolites were mainly related to nucleotides, organic acids and their derivatives, while the downregulated metabolites were mainly related to amino acids, lipids and their derivatives. Flavoromics analysis revealed that 137 metabolites were significantly differentially regulated, particularly garlicky and pungent volatiles were significantly downregulated. Correlation analysis indicated that esters are most closely related to nonvolatile metabolites, and lipids degradation was significantly correlated with volatiles. The results indicated that W. anomalus fermentation is an effective strategy to improve the flavor of black garlic juice.

Enhanced production of gamma-aminobutyric acid in fermented carrot juice by utilizing pectin hydrolysate derived from pomegranate waste

In this study, a functional fermented beverage enriched with gamma-aminobutyric acid (GABA) was produced. To achieve this, the prebiotic abilities of pectin obtained from pomegranate peel and its enzymatic hydrolysates were evaluated. Additionally, a functional fermented beverage enriched with GABA was produced by fermenting carrot juice with pectin hydrolysates. First, pectin was obtained at a yield of 8.91% from pomegranate peels. Pectinase-catalyzed hydrolysis of the obtained pectin was applied using different enzyme concentrations and hydrolysis times, and the effect of these hydrolysates on the growth of Levilactobacillus brevis was determined. Although the Fourier transform infrared (FT-IR) spectra of the resulting hydrolysates were similar, their degree of esterification compared to that of pectin was statistically different (p < .05). Considering the viability analysis and GABA production of L. brevis in the liquid medium supplemented with pectin or its hydrolysate, the hydrolysate obtained by treatment with 400 μL enzyme for 2 h and having a high glucose content (216.80 mg/100 g) was selected for application in fermented carrot juice. During fermentation (24, 48, and 72 h), a remarkable change was observed, especially in the amounts of lactic acid and malic acid, while the amount of GABA in carrot juice varied between 25 and 46 mg/mL and increased with the increase in hydrolysate concentration. It was observed that the total phenolic content and antioxidant activity of carrot juice were highly affected by the hydrolysate concentration. This study demonstrated that pectin hydrolysate obtained from food waste could be a potential prebiotic and could be used in the production of a functional beverage with improved GABA content.

Recent advances of fermented fruits: A review on strains, fermentation strategies, and functional activities

Fruits are recognized as healthy foods with abundant nutritional content. However, due to their high content of sugar and water, they are easily contaminated by microorganisms leading to spoilage. Probiotic fermentation is an effective method to prevent fruit spoilage. In addition, during fermentation, the probiotics can react with the nutrients in fruits to produce new derived compounds, giving the fruit specific flavor, enhanced color, active ingredients, and nutritional values. Noteworthy, the choice of fermentation strains and strategies has a significant impact on the quality of fermented fruits. Thus, this review provides comprehensive information on the fermentation strains (especially yeast, lactic acid bacteria, and acetic acid bacteria), fermentation strategies (natural or inoculation fermentation, mono- or mixed-strain inoculation fermentation, and liquid- or solid-state fermentation), and the effect of fermentation on the shelf life, flavor, color, functional components, and physiological activities of fruits. This review will provide a theoretical guidance for the production of fermented fruits.

Microbial-Derived γ-Aminobutyric Acid: Synthesis, Purification, Physiological Function, and Applications

γ-Aminobutyric acid (GABA) is an important nonprotein amino acid that extensively exists in nature. At present, GABA is mainly obtained through chemical synthesis, plant enrichment, and microbial production, among which microbial production has received widespread attention due to its safety and environmental benefits. After using microbial fermentation to obtain GABA, it is necessary to be isolated and purified to ensure its quality and suitability for various industries such as food, agriculture, livestock, pharmaceutics, and others. This article provides a comprehensive review of the different sources of GABA, including its presence in nature and the synthesis methods. The factors affecting the production of microbial-derived GABA and its isolation and purification methods are further elucidated. Moreover, the main physiological functions of GABA and its application in different fields are also reviewed. By advancing our understanding of GABA, we can unlock its full potential and further utilize it in various fields to improve human health and well-being.

Effect of a Combination of Ultrasonic Germination and Fermentation Processes on the Antioxidant Activity and γ-Aminobutyric Acid Content of Food Ingredients

Whole-grain food ingredients enable the most balanced food products to be obtained, thus forming an important part of a healthy and sustainable diet. Wheat and barley grains are a traditional source of food ingredients for breads, breakfasts, drinks, and snacks in Russia. Such foods are suitable for all ages with many health benefits. However, the modern metropolitan citizen consumes large quantities of refined cereal products, thus impoverishing their diet. An alternative in dietary fortification could be sprouted and fermented food ingredients with an increased nutritional value. The present work was carried out to study the effect of a combination of germination with ultrasound treatment and fermentation with a complex starter of cereal crops on antioxidant activity and γ-aminobutyric acid content of food ingredients with the possibility of using them in the matrix of food products. In order to obtain germinated food ingredients, we used crops with the highest yield in the Ural region (Russia): two samples of soft spring wheat (Triticum aestivum L.) and a sample of spring barley grain (Hordeum vulgare L.). Obtaining food ingredients was divided into successive stages: ultrasonic treatment (22 ± 1.25 kHz) was performed by means of changing power and length of time (245 W/L, intensity for 5 min); germination and fermentation used complex starter “Vivo Probio”. The proposed technology of germination with haunting fermentation of cereal crops resulted in food ingredients with a more uniform distribution of granulometric composition, a low proportion of fine particles (4.62–104.60 µm) (p < 0.05) and large particles (418.60–592.00 µm) (p < 0.05). The particle size range (31.11–248.90 μm) (p < 0.05) was predominant. The germination and fermentation process resulted in 26 to 57% (p < 0.05) lower phytic acid content, 35 to 68% (p < 0.05) higher flavonoid content, 31 to 51% (p < 0.05) higher total antioxidant activity, 42.4 to 93.9% (p < 0.05) higher assimilability, and 3.1 to 4.7 times (p < 0.05) higher γ-aminobutyric acid content, which will allow production of food products with pronounced preventive action. The data was analyzed via one-way ANOVA analysis of variance using the free web-based software. The combination of the germination process with ultrasound treatment and subsequent fermentation with a complex starter can be used to support the development of healthful food products with increased GABA and antioxidant activity.

Optimization of Solid-Phase Lactobacillus Fermentation Conditions to Increase γ-Aminobutyric Acid (GABA) Content in Selected Substrates

The purpose of this study was to optimize conditions of solid-phase fermentation of lactic acid bacteria to enhance GABA contents in grains. Optimal solid-phase fermentation conditions that could enhance the GABA content after fermenting Oryza sativa (brown rice) were investigated by changing the Lactobacillus strain, fermentation temperature, fermentation time, and inoculated bacteria number. Avena sativa, Cicer arietinum, and red and brown Lens culinaris were then fermented using the optimal solid-phase fermentation conditions to measure changes in GABA content and antioxidant activity. As a result of the experiment, the optimal solid-phase fermentation conditions to enhance the GABA contents in grains were: fermentation time, 48 h; amounts of bacteria, inoculating 5% of 1 × 107 CFU/mL of lactic acid bacteria; and fermentation temperature, 36 °C. When fermented under this condition, the GABA content increased from 4.64 mg/g to 6.93 mg/g (49.0%) compared to unfermented raw material. The results of the DPPH and ABTS radical scavenging activity assays confirmed that both the GABA content and radical scavenging activity were increased after fermentation. Such solid fermentation conditions developed in this study can be used to support the development of health functional food materials with enhanced GABA content and antioxidant activity.