Effect of particle size, moisture content, and supplements on selective pretreatment of cotton stalks by Daedalea flavida and enzymatic saccharification.

Harmanpreet Meehnian,Asim K Jana,Mithu Maiti Jana

doi:10.1007/s13205-016-0548-x

Harmanpreet Meehnian, Asim K Jana + Show 1 more

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https://doi.org/10.1007/s13205-016-0548-x

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Abstract

A large amount of cotton stalk waste biomass with high cellulose content are incinerated by the farmers causing air pollution. The high cellulose content of cotton stalks can be converted to fermentable sugars by fungal delignification pretreatment of lignocellulosic biomass and enzymatic saccharification. The effect of particle size, moisture content, and media supplements was studied for delignification of cotton stalks by Daedalea flavida MTCC 145 (DF-2) in solid-state fermentation. The highest lignolytic enzyme activities, optimal lignin degradation 29.88 ± 0.97% (w/w) with cellulose loss 11.70 ± 1.30% (w/w), were observed in cotton stalks at particle size 5 mm with 75% moisture content after 20 days. Cellulolytic enzyme activity increased with decrease in particle size and increased moisture content. The addition of Cu2+, gallic acid, and veratryl alcohol enhanced the lignolytic enzyme production and the lignin degradation. In addition to increased laccase activity, Cu2+ inhibited the cellulolytic activity. Supplements Cu2+ at 0.5 mM/g gave the best results of lignin degradation 33.74 ± 1.17% (w/w) and highest selectivity value (SV) 3.15 after pretreatment. The glucose yield increased to 127.44 ± 4.56 mg/g from 20 day pretreated cotton stalks with Cu2+ supplements, ~threefolds higher than untreated cotton stalks. The study is important for the production of fermentable sugars from cotton stalks residues which can further be utilized in production of bioethanol and other applications.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-016-0548-x) contains supplementary material, which is available to authorized users.

Highlights

The expeditious consumption of non-renewable energy resources has awakened the world to harvest the energy from renewable resources for sustainable growth and development (Tiwari et al 2013)
The bioethanol produced from the food crops, such as corn, has been considered as threat for food security; replacement of it with economical and most abundantly available lignocellulosic biomass mainly agriculture residues is of great interest (Sun and Cheng 2002)
The fungal strains were screened on the basis of their lignocellulolytic abilities and selectivity value (SV) in solid-state fermentation (SSF) during pretreatment

Summary

Introduction

The expeditious consumption of non-renewable energy resources has awakened the world to harvest the energy from renewable resources for sustainable growth and development (Tiwari et al 2013). A pretreatment process is necessary to remove the lignin and reduce the cellulose crystallinity from lignocellulosic biomass Various pretreatment methods, such as physical, chemical and biological methods, are used for delignification of biomass to improve the enzymatic saccharification (Zhang et al 2007). Biotech (2016) 6:235 pretreatment of lignocellulosic biomass, WRF produces cellulolytic enzymes and digest the cellulose for its own growth and metabolism resulting low selectivity value (SV, the ratio of lignin degradation to cellulose loss) (Eriksson et al 1990). The cellulose loss during pretreatment of lignocellulosic biomass by WRF is the major problem, which results in low carbohydrate recovery and low glucose yield after enzymatic saccharification. The present study on pretreatment of cotton stalks by Daedalea flavida MTCC 145 is targeted towards achievement of higher delignification of cotton stalks with minimum cellulose loss, i.e., enhanced SV/recovery of carbohydrates using optimal particle size, moisture content, and supplements

Materials and methods

Results and discussion

Conclusion