Abstract
BackgroundSingle cell oil (SCO) production from lignocelluloses by oleaginous microorganisms is still high in production cost, making the subsequent production of biofuels inviable economically in such an era of low oil prices. Therefore, how to upgrade the final products of lignocellulose-based bioprocess to more valuable ones is becoming a more and more important issue.ResultsDifferently sourced cellulases were compared in the enzymatic hydrolysis of the steam-exploded corn stover (SECS) and the cellulase from the mixed culture of Trichoderma reesei and Aspergillus niger was found to have the highest enzymatic hydrolysis yield 86.67 ± 4.06%. Three-stage enzymatic hydrolysis could greatly improve the efficiency of the enzymatic hydrolysis of SECS, achieving a yield of 74.24 ± 2.69% within 30 h. Different bioprocesses from SECS to SCO were compared and the bioprocess C with the three-stage enzymatic hydrolysis was the most efficient, producing 57.15 g dry cell biomass containing 31.80 g SCO from 327.63 g SECS. An efficient and comprehensive process from corn stover to long-chain α,ω-dicarboxylic acids (DCAs) was established by employing self-metathesis, capable of producing 6.02 g long-chain DCAs from 409.54 g corn stover and 6.02 g alkenes as byproducts.ConclusionsOn-site cellulase production by the mixed culture of T. reesei and A. niger is proven the most efficient in providing cellulase to the lignocellulose-based bioprocess. Three-stage enzymatic hydrolysis was found to have very good application value in SCO production by Trichosporon cutaneum from SECS. A whole process from corn stover to long-chain DCAs via a combination of biological and chemical approaches was successfully established and it is an enlightening example of the comprehensive utilization of agricultural wastes.
Highlights
Single cell oil (SCO) production from lignocelluloses by oleaginous microorganisms is still high in production cost, making the subsequent production of biofuels inviable economically in such an era of low oil prices
Mixed culture Different mixed culture forms of T. reesei and A. niger were tried to identify the optimal form of cellulase production with the highest Filter paper activity (FPA) and the bettered composition
The monoculture of A. niger resulted in high beta-glucosidase activity (BGA) but very low FPA, mainly because A. niger is famous for its high BGA but not as robust as T. reesei in secreting a complete cellulase mixture that can degrade cellulose to monomeric sugars [12, 24]
Summary
Single cell oil (SCO) production from lignocelluloses by oleaginous microorganisms is still high in production cost, making the subsequent production of biofuels inviable economically in such an era of low oil prices. As an agricultural country with more than 1.3 billion people to feed, China has plenty of agricultural wastes or residues that should be utilized in an economic and environmentally friendly way This is good for rural economy and environment protection because the reality is that those agricultural residues are always treated improperly, Single cell oil (SCO) from microorganism is thought to be a desirable alternative oil source to plant oil or animal fat due to the high productivity, the low land requirement, as well as their particular and precise biochemical. Steam explosion produces lots of inhibitors that are resulted from the decomposition of hemicellulose and lignin [11, 14], making T. cutaneum a desirable candidate for SCO production from steam-exploded lignocellulosic materials
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