Selection and optimization of lignocellulosic substrate for laccase production from Pleurotus species

The aim of the current study was to investigate the potential of Pleurotus species for laccase production on different lignocellulosic substrates and determine the optimal levels of physicochemical conditions required for the production. The study was conducted in National Agricultural Biotechnological Research Center, Holetta. The fruiting bodies of fungi were collected based on their morphology and inoculated on potato dextrose agar plate. Six different lignocellulosic substrates were collected and prepared for cultivation of Pleurotus species for laccase production. The highest enzyme production was obtained from bean straw compared to other substrates with an activity of 0.112 U/ml. The best three substrates; bean straw, Eucalyptus sawdust and wheat straw were selected, and a mixture of each of them on equal proportions was tested for laccase production potential. A mixture of Eucalyptus sawdust and bean straw on equal proportion was found to be the best, showing an activity of 0.137 U/ml and hence selected for different parameter optimization. Optimal laccase production (0.292 U/ml) was obtained on the 10th day of incubation period and the optimum temperature and pH were 28°C and 5.5, respectively. Soluble starch and peptone were found to be the most preferred carbon and nitrogen sources for laccase production, respectively. Asparagine and alanine induced more laccase production, with asparagine being the most potent inducer.   Key words: Pleurotus species, lignocellulosic substrates, bean straw, Eucalyptus sawdust, laccase.