In vitro Antioxidant activity of extracellular L-glutaminase enzyme isolated from marine yeast Rhodotorula sp. DAMB1

Abstract

Yeasts from marine ecosystem have been recognized as producers of several bioactive compounds and also for various enzyme productions. The present study mainly focuses on the extracellular production, medium optimization and in vitro antioxidant activity of L-glutaminase enzyme from marine yeasts isolated from marine water samples of the backwaters of Andaman-Nicobar islands, India. A total of 26 marine yeast isolates were recovered using yeast malt agar (YMA) medium. After primary screening using minimal glutamine agar, 4 marine yeast isolates DAMB1, DAMB2, DAMB3 and DAMB4 showed positive enzyme activity. Zones of hydrolysis for DAMB1 and DAMB3 were 40mm and 30mm respectively. Further, secondary screening was done for the two potential yeast isolates at pH 7.6 along with nesslerization for quantitative analysis. Yeast isolate DAMB1 showed highest L-glutaminase enzyme activity of 67%. This was followed by medium optimization for better production of L-glutaminase enzyme. The optimum temperature and pH was 37°C and pH 8 respectively. Optimum carbon source was arabinose and optimum nitrogen source was found to be casein. The potential yeast isolates showed good antioxidant activity too. DAMB1 showed highest DPPH activity of 62% and DAMB2 showed DPPH activity of 47%. The potential yeast isolate was identified as Rhodotorula sp. DAMB1 (Acc. No. MK968443) using 18s rRNA sequencing method.