Streptomyces griseorubens mediated delignification of paddy straw for improved enzymatic saccharification yields

Biological pretreatment of paddy straw was carried out using an actinomycete isolate, identified as Streptomyces griseorubens ssr38, for delignification under solid state fermentation and enhanced sugar recovery by enzymatic saccharification. After 10 days incubation, the inoculated paddy straw was extracted with mild alkali and high absorbance at 205 nm was shown by the extracts indicating the ability of S. griseorubens ssr38 to depolymerize/solubilize lignin to a high extent. Also, almost 25% of depolymerized lignin could be recovered as value-added acid-precipitable polymeric lignin (APPL) as compared to controls. Enrichment in carbohydrate content of inoculated paddy straw following delignification led to a high saccharification efficiency of 97.8% upon enzymatic hydrolysis with Accelerase®1500. The study, therefore, proves the potential of actinomycetes, besides the conventionally used white-rot fungi, for biological pretreatment, in the biomass to bioethanol process, with respect to the high extent of delignification, lignin recovery, cellulose enrichment and very high saccharification efficiency.