Hydrogen bioelectrogeneration with pH-resilient and oxygen-tolerant cobalt apoenzyme-saccharide.

Hydrogenases are enzymes that catalyze the reversible conversion of protons to hydrogen gas, using earth-abundant metals such as nickel and/or iron. This characteristic makes them promising for sustainable energy applications, particularly in clean hydrogen production. However, their widespread use faces challenges, including a limited pH range and susceptibility to oxygen. In response to these issues, SacCoMyo is introduced as an artificial enzyme. SacCoMyo is designed by replacing the native metal in the myoglobin (Myo) scaffold with a hydroxocobalamin (Co) porphyrin core and complemented by a protective heteropolysaccharide-linked (Sac) shell. This engineered protein proves to be resilient, maintaining robust functionality even in acidic environments and preventing denaturation in a pH 1 electrolyte. The cobalt porphyrin core of SacCoMyo reduces the activation overpotential for hydrogen generation. A high turnover frequency of about 2400 H2 s-1 is demonstrated in the presence of molecular oxygen, showcasing its potential in biohydrogen production and its ability to overcome the limitations associated with natural hydrogenases.

Recent advances in lignocellulosic biomass for biofuels and value-added bioproducts - A critical review.

Lignocellulosic biomass is a highly renewable, economical, and carbon-neutral feedstock containing sugar-rich moieties that can be processed to produce second-generation biofuels and bio-sourced compounds. However, due to their heterogeneous multi-scale structure, the lignocellulosic materials have major limitations to valorization and exhibit recalcitrance to saccharification or hydrolysis by enzymes. In this context, this review focuses on the latest methods available and state-of-the-art technologies in the pretreatment of lignocellulosic biomass, which aids the disintegration of the complex materials into monomeric units. In addition, this review deals with the genetic engineering techniques to develop advanced strategies for fermentation processes or microbial cell factories to generate desired products in native or modified hosts. Further, it also intends to bridge the gap in developing various economically feasible lignocellulosic products and chemicals using biorefining technologies.