title: Construction of dextrin and isomaltose-assimilating brewer's yeasts for production of low-carbohydrate beer.
abstract: 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.
authors.affiliation: Department of Biological Sciences, College of Natural Sciences, Chonnam National University, Gwangju, 500-757, South Korea.
authors.forename: Jin-Yeong
authors.initials: JY
authors.lastname: Park
authors.forename: Ja-Yeon
authors.initials: JY
authors.lastname: Lee
authors.forename: Seung-Hyun
authors.initials: SH
authors.lastname: Choi
authors.forename: Hyun-Mi
authors.initials: HM
authors.lastname: Ko
authors.forename: Il-Chul
authors.initials: IC
authors.lastname: Kim
authors.forename: Hwanghee Blaise
authors.initials: HB
authors.lastname: Lee
authors.forename: Suk
authors.initials: S
authors.lastname: Bai
mesh_terms: D001515:Beer / Q000382:microbiology*; D002851:Chromatography, High Pressure Liquid; D003912:Dextrins / Q000378:metabolism*; D005087:Glucan 1,4-alpha-Glucosidase / Q000235:genetics; D006868:Hydrolysis; D007534:Isomaltose / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D013997:Time Factors; D014170:Transformation, Genetic
chemical_list: D003912:Dextrins; D007534:Isomaltose; D005087:Glucan 1,4-alpha-Glucosidase