Development of stress tolerant strain of versatile peroxidase producing fungus for increasing paddy straw digestibility
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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
The present study focused on the development of stress tolerant versatile peroxidase producing fungal strain for enhancing paddy straw digestibility and biogas production. Four standard cultures viz., Coriolus versicolor MTCC 138, Phanerochaete chrysosporium MTCC 787, Pleurotus ostreatus MTCC 142 and Aspergillus oryzae were screened quantitatively and qualitatively for VP production. Qualitative screening indicates the presence of ligninolytic enzymes in three cultures except Aspergillus oryzae. Quantitative screening of the lignolytic cultures showed maximum enzyme activity in Pleurotus ostreatus MTCC 142. Multivariate optimization of VP production in Pleurotus ostreatus MTCC 142 by response surface methodology indicates that maximum manganese dependent versatile peroxidase activity of 1843 U L-1 was achieved on day 5 of incubation, at 20°C, pH 5 while manganese independent versatile peroxidase activity of 973U L-1 was attained on day 10 of incubation, at 20°C, pH 7. The crude enzyme extract produced under optimized conditions was partially purified by ammonium sulphate precipitation, dialysis and column chromatography, which resulted in 4.2 fold purification of VP. Strain improvement studies by mutagenesis resulted in increased laccase and manganese independent versatile peroxidase activity by 4.48% and 19.9%, respectively, as compared to the wild type. Further the effect of pretreatment on paddy straw digestibility with the wild strain of P. ostreatus MTCC 142 resulted in the reduction of lignin and silica content by 28% and 22%, while pretreatment with mutant strain of P. ostreatus MTCC 142 decreased the lignin and silica content by 20% and 6% after 9 days of pretreatment. Biogas production profile of wild and mutant strain of P. ostreatus MTCC 142 showed that paddy straw pretreated for 6 days with mutatnt strain of Pleurotus ostreatus MTCC 142 resulted in increase in biogas production by 58% as compared to control, while paddy straw pretreated with wild strain of Pleurotus ostreatus MTCC 142 showed highest biogas production after 3 days of pretreatrment and indicated an increase of 22% in biogas production.
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Citation
Parmar, Manisha (2020) Development of stress tolerant strain of versatile peroxidase producing fungus for increasing paddy straw digestibility (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.