초록
<P><B>Abstract</B></P> <P>In order to investigate the effect of mating type and ploidy on enzymatic activity and fermentation performance in yeast with multiple δ-integrated foreign genes, eight ploidy series strains were constructed. The initial haploid strain BGL-a was shown to contain about 19 copies of the <I>bgl</I>1 gene. In rich media containing 2% (w/v) sugar the specific activities of BGL-aα were lower than those of BGL-aa or BGL-αα, which indicates the existence of mating type effects. While the maximum OD<SUB>660</SUB> decreased with rising ploidy, the biomass yield showed no significant difference between the eight strains and the specific activities (expressed as U/mL or U/mg DCW) showed little to no variation. When cellobiose was used as the carbon source and β-glucosidase substrate, β-glucosidase was expressed more quickly and at higher levels than in glucose-containing media. The maximum specific activitiy values obtained were 19.07U/mL and 19.39U/mL for BGL-αα and BGL-aa, repsectively. The anaerobic biomass and ethanol-producing performance in rich media containing 10% cellobiose showed no significant difference among the eight strains. Their maximal ethanol concentrations and corresponding yields ranged from 40.27 to 43.46g/L and 77.56 to 83.71%, respectively. When the acid- and alkali-pretreated corncob (10% solids content) was used, the diploid BGL-aα fermented the best. When urea was used as the only supplemented nutrient, the ethanol titer and yield were 35.65g/L and 83.69%, respectively, while a control experiment using industrial Angel yeast with exogenous β-glucosidase addition gave values of 37.93g/L and 89.04%. The combined effects of δ-integration of <I>bgl</I>1, ploidy and mating type result in BGL-aa or BGL-αα being the optimal choice for enzyme production and BGL-aα being more suitable for cellulosic ethanol fermentation. These results provide valuable information for future yeast breeding and utilization efforts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> BGL-a with 19 copies δ-integrated <I>bgl</I> was gained and then seven ploidy series strains. </LI> <LI> Mating type effect: specific activity of BGL-aα was lower than that of BGL-aa or -αα. </LI> <LI> Maximum OD<SUB>660</SUB> decreased with ploidy and specific activity increased with ploidy. </LI> <LI> No typical mating type and ploidy effect on ethanol production in 10% cellobiose. </LI> <LI> BGL-aα produced ethanol (titer 35.65g/L and yield 83.69%) from pretreated corncob. </LI> </UL> </P>