Many countries have their biofuel policy programs in place as part of their overall strategy to achieve sustainable development. Among biofuels, bioethanol as a promising alternative to gasoline is of substantial interest. However, there is limited availability of a sufficient quantity of bioethanol to meet demands due to bottlenecks in the present technologies to convert non-edible feedstocks, including lignocelluloses. This review article presents and critically discusses the recent advances in the pretreatment of lignocellulosic biomass, with a focus on the use of green solvents, including ionic liquids and deep eutectic solvents, followed by enzymatic saccharification using auxiliary proteins for the efficient saccharification of pretreated biomass. Different techniques used in strain improvement strategies to develop hyper-producing deregulated lignocellulolytic strains are also compared and discussed. The advanced techniques employed for fermentation of mixed sugars contained in lignocellulosic hydrolysates for maximizing bioethanol production are summarized with an emphasis on pathway and transporters engineering for xylose assimilation. Further, the integration of different steps is suggested and discussed for efficient biomass utilization and improved ethanol yields and productivity.

A Plackett-Burman design was employed to evaluate the effect of different culture conditions associated with xylanase and cellulase production by the fungus C. cinerea RM-1 NFCCI 3086 using agro-residues as substrate. Eight variables were assessed for their significance on xylanase and cellulase production under solid state fermentation. The optimal culture conditions for xylanase production were developed by maintaining the variables of temperature, incubation period, substrate concentration, particle size, inoculum size, and inoculum age at their higher levels, while keeping pH and moisture ratio at their lower levels. For cellulase production, temperature, incubation period, substrate concentration, inoculum size, and inoculum age were fixed at their higher levels, and pH, particle size, and moisture level were kept at their lower levels. Of the eight variables, temperature, incubation period, and pH had significant influence on xylanase and cellulase production. These three variables can be further optimized for increased enzyme production.

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