Multifaceted screening and optimization of laccase-producing rhizospheric yeast for enhanced biosynthesis of laccase enzyme

Abstract

Laccase is a unique, environmentally friendly biological catalyst with a wide range of applications due to its prolific activities. Yeasts were isolated from the rhizosphere soil and screened for their ability to produce laccase using 0.04% guaiacol. The isolates with higher laccase activity were optimized using temperature (30 - 50 °C), pH (4 - 7), inoculum volume (3 - 9 mL), substrate concentration (1 – 6 M) and copper sulphate (0.2 - 0.8 mM). Furthermore, the best conditions in which laccase was optimally produced were used for laccase production. Data obtained were then subjected to one-way analysis of variance following Duncan’s multiple range test at p ≤ 0.05. The result of this study showed that four laccase-producing yeasts of the genera Candida and Yarrowia were isolated and identified from the samples. Of all the four isolates, Yarrowia galli (0.0953 µ/mL) and Candida albicans (0.0493 µ/mL) had the highest enzyme activity from the quantitative enzyme assay. However, Y. galli produced the highest laccase yield of 0.0396 µ/mL at day 7 under the optimal conditions in which laccase had the highest activity. These conditions are pH 6.0, temperature 30 o C, inoculum volume 6 mL, guaiacol concentration 4 M and copper sulphate concentration 0.4 mM. We recommend these conditions for laccase production by Y. galli . • The rhizosphere is a region to isolate yeast with high enzymatic activity • Y. galli is the most effective laccase-producing yeast • Y. galli optimally produced laccase at pH 6.0, temperature 30 o C, inoculum volume 6 mL, guaiacol concentration 4 M and copper sulphate concentration 0.4 mM