Characterisation of Amylolytic Brewing Yeast

Abstract

Amyioiytic brewing yeast can be used for the production of low carbohydrate beer and for maximizing fermentation efficiency. In this paper we describe the characterisation of amyioiytic brewing yeast in which the STA2 (DEX1) gene, which codes for an extracellular glucoamylase, was cloned under two different promoters; PGK (phosphoglycerate kinase) and GPD1 (sn-glycerol -3-phosphate dehydrogenase) present on episomal plasmids. Both amyioiytic strains were shown to ferment and degrade wort as efficiently as the control strain supplemented with an exogenous commercial glucoamylase, despite reduced intracellular glycogen levels (30% of wild-type). However, the nature of the promoter on the expression plasmid was shown to influence both the growth rate of the amyioiytic strains and the stability of the plasmids during non-selective growth. One of the strains containing plasmid pDVX4 {GPD promoter) was found to show high levels of stability when tested in ten successive pilot scale (8Hlitre) fermentations.

ORIGINAL RESEARCH: Chromosomal integration of both an α-amylase and a glucoamylase gene inSaccharomyces cerevisiaefor starch conversion

“…18,19 Heterologous production of amylolytic enzymes in S. cerevisiae has been achieved almost exclusively by the use of episomal vectors. 15,[20][21][22][23][24] An undesirable feature of episomal expression vectors, however, is their instability with gradual loss of the acquired genetic information in subsequent generations. 25,26 Chromosomal integration, like that used in this investigation, enables cloning of multiple genes as a more stable alternative.…”

Evolución genómica por diseño molecular de levaduras industriales

“…-Aumento del contenido alcohólico 1% (v/v) y disminución del contenido energético. Zhang et al, 2008Lancashire et al, 1989Vakeria et al, 1996 Objetivos específicos para levaduras panaderas…”