Screening Of High β-glucosidase Producing Strains And The Effect Of β-glucosidase On The Bound Aroma In Wine

β-glucosidases is the key enzyme in improvement mechanism of flavor, and it is important to improve the wine aroma, they also can be applied for flavor enhancement in beverage and food industries. Domesticβ-glycosidase were all rely on foreign enzyme company, its price is expensive and not suitable for industrial production, thus there is not yet appeared for the product domestic. Screening ofβ-glucosidase with independent intellectual property rights which keep high enzyme activity in the brewing environment from nature is an effective way. It can improve the flavour of wines and save the cost of enzymes.1. A new method named colour-display method in 96 orifice plate in the screening of strains producingβ-glucosidase was developed about substrate of p-NPG, which was applied in the rapid screening of strains producingβ-glucosidase. After the determination of enzyme activity, three strains showed higer activities. One strain with the highest P-glucosidase activity was used as starting strain for future study. By observing the morphology characteristics and analyzing the 18S rDNA sequence of the strain, the strain was identified as Aspergillus niger.2. This paper was to verify the effects of P-glucosidases from different strains on the bound aroma in Muscat grape by gas chromatography-tradem mass spectrometry (GC-MS). The results showed that P-glucosidase hydrolysis produce typical compounds include terpenoids, alcohols, lipid. P-glucosidases from Aspergillus niger had much more aroma compounds than others. Terpenoids were the most abundant, accounting for 85.91% of the total concentration. Therefore,β-glucosidases from Aspergillus niger may significantly improvement to hydrolyse glycoconjugated aroma compounds,β-glucosidases from Aspergillus niger can improve the flavor of wine. Such terpenoids can give wine special aroma, and the differences provide scientific basis for the directional characteristics of wine aroma.3. In order to enhance enzyme activity of the strain, Low-energy ion implantation was employed to strain and the fermentation conditions and fermentation mediun were optimized. The optimum was obtained by experiments, that is, wheat bran 4%, (NH4)2SO40.2%, urea 0.2 %, KH2PO40.1%, MgSO4·7H2O 0.04%, CaCl20.04%. The optimized cultivation conditions were as follows:20 mL medium in 250 mL conical flask,180r/min,30℃,β-glucosidases enzyme activity of the strain increased 2.26 times under low-energy ion implantation and optimized cultivation cultivation after 7 days'fermentation, reached 27.63 IU/mL. which is higher than previously reported strains of bacteria, yeast.4. In order to examine the enzyme is suitable for wine. The key enzymes were purified by three-step procedure of ammonium sulfate precipitation, QFF-Sepharose, and Superdex-300 purification. SDS-PAGE showed the molecular mass of theβ-glucosidases was 116 kDa. The optimum temperature for the enzyme is 50℃, The optimum pH is 5.0, it has certain lolerability for alcohol. Cu2+could inhibit the acitivity of theβ-glucosidases.