Assessment of β-D-glucosidase activity and bgl gene expression of Oenococcus oeni SD-2a

Bioprospecting Indigenous Oenococcus oeni Strains from Chinese Wine Regions: Multivariate Screening for Stress Tolerance and Aromatic Competence

Malolactic fermentation (MLF), an essential enological process for wine deacidification and aroma development, is predominantly mediated by Oenococcus oeni (O. oeni). This investigation characterized 170 indigenous O. oeni isolates from two principal Chinese viticultural regions (Yinchuan, Ningxia, and Changli, Hebei) through polyphasic analysis. Forty-nine strains demonstrating genetic potential for efficient malate metabolism and biosafety compliance (absence of ethyl carbamate and biogenic amines genes) were subjected to adaptive laboratory evolution under enologically relevant stress conditions. Comparative evaluation with the superior indigenous strain SD-2a revealed eight stress-adapted isolates exhibiting superior MLF kinetics, completing L-malic acid degradation in Marselan wine. Solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) profiling identified three isolates' (3-31, 9-10, and 9-50) significant enhancement of key fermentation aromas in experimental fermentations. These oenologically adapted indigenous strains demonstrate promising potential as regional-specific starter cultures, providing a scientific foundation for developing terroir-expressive winemaking practices and optimizing microbial resources in China's wine industry.

Localization, purification, and characterization of a novel β-glucosidase from Hanseniaspora uvarum Yun268

β-Glucosidase is a key enzyme that hydrolyzes nonvolatile glycosylated precursors of aroma compounds and enhances the organoleptic quality of wines. In this study, a novel β-glucosidase from Hanseniaspora uvarum Yun268 was localized, purified, and characterized. Results indicated that β-glucosidase activity was mainly distributed within the cells. After purification via ammonium sulfate precipitation combined with chromatography, β-glucosidase specific activity increased 8.36 times, and the activity recovery was 56.90%. The enzyme had a molecular mass of 74.22 kDa. It has a Michaelis constant (K_m ) of 0.65 mmol/L, and a maximum velocity (V_max ) of 5.1 nmol/min under optimum conditions; and K_m of 0.94 mmol/L, and V_max of 2.8 nmol/min under typical winemaking conditions. It exhibited the highest activity at 50°C and pH 5.0 and was stable at a temperature range of 20-80°C and pH range of 3.0-8.0. The enzyme has good tolerance to Fe³⁺ , especially maintaining 93.68% of its activity with 10 mmol/L of Fe³⁺ . Ethanol (<20%) and glucose (<150 g/L) inhibited its activity only slightly. Therefore, β-glucosidase from H. uvarum Yun268 has excellent biochemical properties and a good application potential in winemaking. PRACTICAL APPLICATION: Winemaking is a biotechnological process in which exogenous β-glucosidase is used to overcome the deficiency of endogenous β-glucosidase activity in grapes. By localizing, purifying, and characterizing of β-glucosidase from Hanseniaspora uvarum Yun268, it is expected to reveal its physical and chemical characteristics to evaluate its oenological properties in winemaking. The results may provide the basis for promoting the release of varietal aroma and improving wine sensory quality in the wine industry.

Probiotic properties of lactic acid bacteria isolated from traditionally prepared dry starters of the Eastern Himalayas

The Himalayan people prepare dry and oval to round-shaped starter cultures to ferment cereals into mild-alcoholic beverages, which contain lactic acid bacteria (LAB) as one of the essential microbiota. There is no report on probiotic characters of LAB isolated from dry starters. Hence, we screened the probiotic and some functional properties of 37 LAB strains isolated from dry starters of the Eastern Himalayas viz. marcha, phab, paa, pee and phut. About 38% of the LAB strains showed high survival rate (> 50%) at pH 3 and 0.3% bile salts. Enterococcus durans BPB21 and SMB7 showed the highest hydrophobicity percentage of 98%. E. durans DMB4 and SMB7 showed maximum cholesterol assimilation activity. About 65% of the LAB strains showed the ability to produce β galactosidase. Majority of the strains showed phytase activity, whereas none of the strain showed amylase activity. About 86% of LAB strains showed an optimum tolerance of 10% ethanol concentration. Genetic screening of some probiotic and functional marker genes have also been analysed. The occurrence of clp L gene, agu A gene (survival of gastrointestinal tract conditions), apf, mub1 and map A gene (adhesion genes) was higher compared to other genes. The occurrence of bsh gene (bile salt tolerance) was detected in Pediococcus pentosaceus SMB13-1 and Enterococcus faecium BPB11. Gene ped B for pediocin with amplicon size of 375 bp was detected in E. durans DMB13 and Pediococcus acidilactici AKB3. Detection of nutritional marker gene rib A and fol P in some strains showed the potential ability to synthesize riboflavin and folic acid. LAB with probiotic and functional properties may be explored for food industry in future.