基因工程菌株VB84酵母的啤酒发酵特性研究

Study on tne brewing characteristics 0f gene engineering yeast strain VB84.

5株通过质粒转导而获得β-葡聚糖酶基因的下面啤酒酵母,都能在啤酒主发酵期内将麦芽汁中90％以上的β-葡聚糖分解.其中VB84菌株能在4天内分解β-葡聚糖94.1％.它在啤酒发酵过程中的繁殖速率、细胞浓度、降糖速率和最终发酵度均保持正常.随着β-葡聚糖的分解,啤酒的易滤性得到明显改善,V_(max)值提高56.3％.对β-葡聚糖凝胶的分解速率略低于对溶胶态β-葡聚糖的分解.啤酒的各项质量指标正常,对泡持性没有影响.

Five strains of Saccharomyces uvarum,having obtained the β-glucanase gene by plasmid transduc-tion,were all able to decompose P-glucan over 90 per cent in the wort during the main fermentation of beer brewing. Strain VB84 was able to decompose P-glucan about 94. 1 per cent in 4 days,its reproductive rate,cell population ,sugar concentration reducing rate and attenuation final degree were all normal during the brewing process. With the decomposition of P-glucan,the filterability of beer was improved conspicuously and the Vmax value increased by 56. 3 per cent. The velocity and the efficiency of decomposing p-glucan gel were slightly lower than that of β-glucan sol. Each quality index of the beer was normal and the foam retention was not affected at all.