TORULASPORA DELBRUECKII: A NOVEL YEAST ISOLATE FOR L- PHENYLACETYLCARBINOL (L-PAC) PRODUCTION

The current study describes the biosynthesis of L-phenylacetylcarbinol (L-PAC) by Torulaspora delbrueckii using molasses in shake flasks. The yeast isolates were screened for temperature tolerance, solvent stress and carboligase activity. Solvent resistant and thermotolerant Torulaspora delbrueckii yeast was selected which was identified through sequencing of their rDNA R26, R18 and ITs regions. The incubation time of 24hrs, incubation temperature of 30oC, total sugar at 17% and pH of the medium at 5.5 with 10% inoculum size were found to be optimum for maximum production of L-PAC. Urea and Di-amonium Phosphate were selected as the best nitrogen sources for this purpose. The wild strain of T. delbrukii was subjected to random mutagenesis through UV, nitrous acid and ethyl methanesulfonate (EMS) treatment. Nitrous acid mutant treated for 40 min was selected after quantitative screening for further optimization. After mutagenesis, optimum pH and incubation time of Torulaspora delbrueckii were shifted to 5.0 and 18hrs while other parameters were same as for wild strain. After optimization of process parameters, nitrous acid mutant of T. delbrukei produced 7.99 g/l L-Phenylacetyl carbinol L-PAC as compared to 6.44 g/l of L-PAC from the wild strain. Hence, the yield of this strain was enhanced significantly after mutagenesis so the mutant strain of Torulaspora delbrueckii can be used in the industry for enhanced production of an important pharmaceutical ingredient, L-PAC.