초록
<P><B>Abstract</B></P> <P>This work reports ultrasound–induced enhancement of astaxanthin production in batch fermentation using wild strain of <I>P. rhodozyma</I> MTCC 7536. The methodology adopted in this study comprises of statistical optimization of the medium and fermentation parameters, followed by application of sonication at optimized conditions. <I>P. rhodozyma</I> fermentation at conditions of 20 g/L glucose, pH 4.4, temperature 21 °C, 4% v/v inoculum, shaking at 205 rpm with nitrogen sources of (NH<SUB>4</SUB>)<SUB>2</SUB>SO<SUB>4</SUB> and yeast extract yielded 6.8 mg/L or 1360 μg/g DCW astaxanthin in 84 h. Application of 33 kHz and 140 kPa sonication at 10% duty cycle in final 12 h of fermentation enhanced the astaxanthin yield to 8.6 mg/L or 1728 μg/g DCW, which is higher than several mutant strains reported in literature. These results are essentially manifestations of intense microturbulence generated by sonication in fermentation mixture.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Optimization of medium and fermentation conditions for wild strain of <I>P. rhodozyma.</I> </LI> <LI> Post optimization astaxanthin production = 6.8 mg/L or 1360 μg/g DCW. </LI> <LI> Fermentation with 33 kHz sonication in three stages (12 h each) at optimized conditions. </LI> <LI> Maximum astaxanthin yield with sonication = 8.6 mg/L or 1728 μg/g DCW. </LI> <LI> Yield enhancement attributed to intense microturbulence generated by sonication. </LI> </UL> </P>