Park Jin-Yeong, Lee Ja-Yeon, Choi Seung-Hyun, Ko Hyun-Mi, Kim Il-Chul, Lee Hwanghee Blaise, Bai Suk
Department of Biological Sciences, College of Natural Sciences, Chonnam National University, Gwangju, 500-757, South Korea.
Biotechnol Lett. 2014 Aug;36(8):1693-9. doi: 10.1007/s10529-014-1530-5. Epub 2014 Apr 16.
Most Saccharomyces spp. cannot degrade or ferment dextrin, which is the second most abundant carbohydrate in wort for commercial beer production. Dextrin-degrading brewer's bottom and top yeasts expressing the glucoamylase gene (GAM1) from Debaryomyces occidentalis were developed to produce low-carbohydrate (calorie) beers. GAM1 was constitutively expressed in brewer's yeasts using a rDNA-integration system that contained yeast CUP1 gene coding for copper resistance as a selective marker. The recombinants secreted active glucoamylase, displaying both α-1,4- and α-1,6-debranching activities, that degraded dextrin and isomaltose and consequently grew using them as sole carbon source. One of the recombinant strains expressing GAM1 hydrolyzed 96 % of 2 % (w/v) dextrin and 98 % of 2 % (w/v) isomaltose within 5 days of growth. Growth, substrate assimilation, and enzyme activity of these strains were characterized.
大多数酿酒酵母不能降解或发酵糊精，糊精是商业啤酒生产麦芽汁中第二丰富的碳水化合物。为了生产低碳水化合物（低热量）啤酒，开发了表达西方德巴利酵母葡糖淀粉酶基因（GAM1）的降解糊精的下面发酵型和上面发酵型啤酒酵母。使用包含编码铜抗性的酵母CUP1基因作为选择标记的rDNA整合系统，使GAM1在啤酒酵母中组成型表达。重组体分泌活性葡糖淀粉酶，其同时具有α-1,4-和α-1,6-去分支活性，可降解糊精和异麦芽糖，因此可以将它们用作唯一碳源进行生长。其中一个表达GAM1的重组菌株在生长5天内水解了2%（w/v）糊精的96%和2%（w/v）异麦芽糖的98%。对这些菌株的生长、底物同化和酶活性进行了表征。
