Pretreatment of cotton stalks by synergistic interaction of Daedalea flavida and Phlebia radiata in co-culture for improvement in delignification and saccharification

•Lignolytic enzyme activities enhanced in D. flavida and P. radiata co-culture.•D. flavida and P. radiata co-culture increased delignification efficiency.•Utilization of hemicellulose as carbon source resulted high cellulose recovery.•Co-culture pretreated cotton stalks yielded higher glucose than monoculture.•Pretreatment time reduced in co-culture compared to monoculture.

Selective lignin degrading white rot fungi Daedalea flavida MTCC 145 (DF-2) and Phlebia radiata MTCC 2791 (PR) interacted synergistically in co-culture to enhance the lignolytic enzymes production during pretreatment of cotton stalks in solid state fermentation. The peak activity of laccase increased to 14.19 ± 0.85 IU g−1 solid on fifteenth day of pretreatment by co-culture, higher than three folds and eight folds to the pretreatment by monoculture of DF-2 and PR respectively. Increase in peak activity of MnP was observed in co-culture compared to its activity in monoculture of PR, whereas additive effect of LiP activity was observed in co-culture. Due to increase in lignolytic activities, lignin degradation increased during pretreatment in co-culture. Lignin degradation was 35.13 ± 1.66% (w/w) after 20 days pretreatment with co-culture. Lignin degradation was 36.29 ± 1.21% (w/w) and 31.02 ± 1.27% (w/w) with DF-2 and PR respectively after 40 days pretreatment, which showed significant reduction of pretreatment time to half in co-culture. The glucose released after enzymatic hydrolysis of 20 days co-culture pretreated cotton stalks 142.88 ± 5.39 mg g−1, was higher than glucose released 117.09 ± 2.26 and 79.21 ± 1.86 mg g−1 from DF-2 and PR pretreated stalks, respectively. Cotton stalks were characterized by FT-IR, SEM, XRD and TGA-DTG to confirm the results.