Lignocellulosic biomass represents perhaps the most abundant renewable resource with a potential to replace fossilbased feedstock for sustainable energy, chemical and materials production. Among the three chief lignocellulosic biomass components (i.e. cellulose, hemicellulose and lignin), lignin is a macromolecule with an aromatic skeleton with a variety of functional groups (e.g. hydroxyl, methoxy, carbonyl, double bond) and carries a higher energy density. The unique structure makes lignin an intriguing substrate for energy, chemicals and materials productions. However, the high molecular weight and complex macromolecular structure have made lignin a challenging substrate to be transformed by many conversion methods. Microbial enzyme degradation and modification of lignin have been subjected to a significant amount research in the last a few decades. Yet so far little success has been demonstrated to merit the use of enzymatic technology for lignin transformation at a commercial scale. This paper provides an updated review of the development of lignin degrading/modifying enzymes with an emphasis on identifying the key barriers and challenges toward practical applications of microbial enzymes for lignin valorization with a hope to generate new insights and direction that can overcome these challenges. Jou Chin Chan received her B.Sc. in Chemical Engineering in 2014 from Universiti Malaysia Sarawak (Malaysia). She is currently pursuing her Ph.D. at the Voiland School of Chemical and Biological Engineering, Washington State University under the supervision of Professor Xiao Zhang. Her current research includes the understanding of enzymatic lignin depolymerization. Michael Paice has over 40 years of experiences in the Canadian pulp and paper industry and is currently principle of Michael Paice & Associates (MP&A), based in Richmond, BC, providing sustainable environmental solutions for several industrial and government clients.

DeoR-type helix-turn-helix (HTH) domain proteins are transcriptional regulators of sugar and nucleoside metabolism in diverse bacteria and occur in select archaea. In the model archaeon , previous work implicated GlpR, a DeoR-type transcriptional regulator, in transcriptional repression of and the gene encoding the fructose-specific phosphofructokinase () during growth on glycerol. However, the global regulon governed by GlpR remained unclear. Here we compared transcriptomes of wild type and Δ mutant strains grown on glycerol and glucose to detect significant transcript level differences for nearly 50 new genes regulated by GlpR. By coupling computational prediction of GlpR binding sequences with and DNA binding experiments, we determined that GlpR directly controls genes encoding enzymes in fructose degradation, including fructose bisphosphate aldolase, a central control point in glycolysis. GlpR also directly controls other transcription factors. In contrast, other metabolic pathways appear to be under indirect influence of GlpR. experiments demonstrated that GlpR purifies as a tetramer that binds the effector molecule fructose-1-phosphate (F1P). These results suggest that GlpR functions as a direct negative regulator of fructose degradation during growth on carbon sources other than fructose, such as glucose and glycerol, and that GlpR bears striking functional similarity to bacterial DeoR-type regulators.Many archaea are extremophiles, able to thrive in habitats of extreme salinity, pH and temperature. These biological properties are ideal for applications in biotechnology. However, limited knowledge of archaeal metabolism is a bottleneck that prevents broad use of archaea as microbial factories for industrial products. Here we characterize how sugar uptake and use is regulated in a species that lives in high salinity. We demonstrate that a key sugar regulatory protein in this archaeal species functions using molecular mechanisms conserved with distantly related bacterial species.

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