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Lignin is an aromatic compound found as a major component of plant cell wall and therefore, present abundantly in nature as a renewable resource. Due to its organic nature, it has the potential to serve as feedstock for value addition to sustainable bioproducts. Under biorefinery concept, each of the plant biomass components viz. cellulose, hemicellulose, and lignin must be converted to some or the other products. Thus, development of different strategies to valorize lignin for chemicals other value-added products can remove the economic constraint on bioethanol-based biorefineries. However, lignin is highly heterogenous than its counterparts and therefore, very recalcitrant to bioconversion making its biovalorization very difficult. To fully utilize the potential of lignin, it is necessary to understand its degradation process and develop efficient biochemical/microbial strategies to achieve cost-effective lignin bioconversion. In recent times, many innovations have taken place in sustainable microbial utilization and bioconversion of lignin. Therefore, this paper focuses on the progress made in lignin biotransformation's for production of bio-based products, chemicals, and bioenergy in the context of biorefinery concept, with a critical perspective on biotechnological advancements, challenges, and future needs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal pretreatment is a sustainable approach for the recovery of XOS. • XOS and GOS of 23.7 and 18.3% respectively was obtained under best conditions. • Conduritol B epoxide served as inhibitor for controlled hydrolysis to get cellobiose. • After controlled hydrolysis 174 mg of cellobiose was obtained per gram of biomass. Globally, the demands for sustainably sourced functional foods like prebiotic oligosaccharides have been constantly increasing. This study assessed the potential of pineapple leaves (PL) as lignocellulosic feedstock for sustainable production of cellulose and hemicellulose-derived oligosaccharides through its hydrothermal pretreatment (HT) followed by controlled enzymatic hydrolysis. PL was subjected to HT at 160, 175, and 190 °C for 20, 30, 60, and 90 min without any catalyst for xylooligosaccharide (XOS) production, whereas, the resulting solid content after HT was subjected to controlled enzymatic hydrolysis by commercial cellulase using conduritol B epoxide (0.5–5 mM) for glucooligosaccharides (GOS) production. HT at 160 °C for 60 min resulted in maximum yield of XOS and GOS at 23.7 and 18.3 %, respectively, in the liquid phase. Controlled enzymatic hydrolysis of HT treated (160 °C) PL solids for 20 and 30 min yielded ∼ 174 mg cellobiose/g dry biomass within 24 h, indicating overall high oligosaccharide production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal combined with mild acid allowed the recovery of xylooligosaccharides. • XOS yield of 67.79% was obtained with 5% gluconic acid at 160 °C for 60 min. • Glucose obtained after enzymatic hydrolysis was used for the production of BC. • BC production with XOS can be integrated for sustainable circular bioprocess. A hydrothermal process is a sustainable approach for biorefinery leading to conversion of lignocellulosic (LC) biomass into value-added products. This study is based on the production of xylooligosaccharides (XOS) from pineapple leaves (PL) waste by using mild acid like gluconic acid (GA). GA, when used as catalyst in hydrothermal process to produce XOS the yield improved. The above process can be integrated with bacterial cellulose (BC) production bioprocess via Komagataeibacter europaeus 14,148 where gluconic acid is produced as by-product. Maximum XOS (2–5 degree of polymerisation) yield of 67.79 % in the liquid fraction was obtained via hydrothermal treatment at 160 °C for 60 min with 5% gluconic acid concentration. It is based on the selective solubilization of hemicellulose fraction. Enzymatic hydrolysis of GA hydrothermally pretreated solid fraction of PL biomass gave 14.5 g/L glucose with 5% solid loading and 10 FPU/gds enzyme loading which was employed for Bacterial cellulose production. [ABSTRACT FROM AUTHOR]

Present study was focused on cellulase production from an indigenously isolated filamentous fungal strain, identified as Penicillium oxalicum . Initially, cellulase production under submerged fermentation in shake flasks resulted in cellulase activity of 0.7 FPU/mL. Optimization of process parameters enhanced cellulase production by 1.7-fold and resulted in maximum cellulase activity of 1.2 FPU/mL in 8 days. Cellulase production was successfully scaled-up to 7 L fermenter under controlled conditions and incubation time was reduced from 8 days to 4 days for achieving similar cellulase titer. Optimum pH and temperature for activity of the crude enzyme were pH 5 and 50 °C, respectively. At 50 °C the produced cellulase retained approximately 50% and 26% of its activity at 48 h and 72 h, respectively. Hydrolytic efficiency of P. oxalicum was comparable to commercial cellulase preparations which indicate its great potential for application in the lignocellulose hydrolysis. [ABSTRACT FROM AUTHOR]