초록
<P><B>Abstract</B></P> <P>The aim of the present work is to develop an osmotolerant yeast strain with high lactose utilization and further use it to ferment lactose rich whey permeate for high ethanol titer and to reduce energy consumption. Ethanol production and growth rate of selected MTCC 1389 strain were quite high in whey containing lactose up to 150g/L but it remains constant in lactose concentration (200g/L) as cells encountered osmotic stress. Thus, strain MTCC 1389 was used for an adaptation to lactose concentration 200g/L for 65days and used further for fermentation of lactose rich whey. Fermentation with an adapted <I>K. marxianus</I> MTCC 1389 strain in laboratory fermenter resulted in ethanol titer of 79.33g/L which is nearly 17.5% higher than the parental strain (66.75g/L). Expression analysis of <I>GPD1, TPS1</I>and <I>TPS2</I> found upregulated in lactose adapted <I>K. marxianus</I> strain as compared to the parental strain. These results suggest that an adapted <I>K. marxianus</I> strain accumulates glycerol and trehalose in response to lactose stress and improve osmotolerance in <I>K. marxianus</I> cells. Thus, the study illustrates that evolutionary engineering is an efficient strategy to obtain a superior biofuel yeast strain, which efficiently ferments four-fold concentrated cheese whey.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A robust dairy yeast strain was obtained by adaptation to lactose rich whey. </LI> <LI> High ethanol titer and productivity were obtained by repeated batch fermentation. </LI> <LI> <I>GPD1</I> plays role in osmoadaptation of <I>K. marxianus</I> strain in lactose rich whey. </LI> <LI> Efficient ethanol production from whey without external nutrient supplementation in media. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>