Isolation, Screening and Characterization of Efficient Lignocellulose Degrading Actinomycetes for Crop Residue Management

Abstract

Ever increasing demand for food made the farming community to adopt intensive agricultural practices leading to a corresponding rise in crop residue production which has to be managed judiciously for by incorporating it in-situ and ex-situ for converting it into compost instead of burning. Faster decomposition of crop residue in the field and production of compost, efficient microbial consortium needs to be developed. To develop efficient decomposing consortium, it requires a variety of lignin, cellulose, hemicelluloses and pectin decomposers. Hence, a study was conducted to isolate decomposers from natural habitat and characterise them to get the efficient ones for developing better consortium for faster decomposition of crop residues. A total of 75 actinomycetes isolates, obtained from 177 various decomposing substrates from natural habit of different parts of Andhra Pradesh. These isolates were primarily screened for in-vitro lignin and cellulose degradation potential. Among these, 52 isolates showed cellulose degradation ability by forming the zone of clearance on carboxy methyl cellulose plates and 29 isolates showed the lignin degradation ability. Among these 75 isolates, 21 have shown both lignin and cellulose degrading ability. Hence, these isolates were quantitatively screened by enzyme assays viz. cellulase, lignin peroxidase, laccase and xylanase activity by using spectrophotometer. Results of secondary screening shows that highest cellulase enzyme activity was shown by LCDA-22 (62.153 U/mL) and LCDA-36 (60.93 U/mL), highest xylanase enzyme activity was recorded by LCDA-1 (39.753 U/mL) and LCDA-22 (39.281 U/mL), highest Laccase enzyme activity was shown by LCDA-22 (579.167U/mL) and LCDA-1 (509.167U/mL), then the highest lignin peroxidase enzyme activity was observed in LCDA-22 (5.064 U/mL) and LCDA-1 (5.007 U/mL). These 21 isolates were characterized morphologically and biochemically, found that they bear powdery growth with white to ash-coloured mycelia with spiral chains of spores and has shown positive results for utilization of different sugars viz. glucose, arabinose, mannitol, sucrose and starch. Based on these results LCDA-1, LCDA-22, LCDA-36, LCDA-40 and LCDA-67 were identified as potential isolates for lignocellulose degradation can be better utilized for developing efficient decomposing consortium. Although lignocellulose-degrading microbes are already well known, this study looks at actinomycetes from a variety of agro-residues in Andhra Pradesh, which hasn’t been explored much. It focuses on finding strains that can produce multiple enzymes, making them more useful in real-world applications than those with just one function for sustainable agriculture.