Fungal cellulases: protein engineering and post-translational modifications

Effect of cellulase on antioxidant activity and flavor of Rosa roxburghii Tratt

Cellulase can increase the soluble dietary fiber (SDF) content in Rosa roxburghii Tratt (RRT), but the effects on polyphenol content, bioactivity, and flavor are unknown. This study analyzed the changes in SDF content, total phenolic content, antioxidant activity and flavor before and after cellulase treatment. Cellulase treatment increased the SDF and total phenolic content of RRT by 13 % (P < 0.05) and 25.68 % (P < 0.05), respectively, and increased the antioxidant activity. HS-GC-IMS identified a total of 42 volatile compounds present, and ROAV analysis revealed that the characteristic aroma compounds of RRT were mainly aldehydes, alcohols, and ethers. The electronic nose and tongue results were consistent with the HS-GC-IMS analysis, indicating the positive effect of cellulase on the quality of RRT. Cellulase treatment significantly improved the oxidative activity and flavor performance of RRT. These results of RRT, providing practical guidance for improving the flavor and product quality.

Engineering of glycoside hydrolase family 7 cellobiohydrolases directed by natural diversity screening

Protein engineering and screening of processive fungal cellobiohydrolases (CBHs) remain challenging due to limited expression hosts, synergy-dependency, and recalcitrant substrates. In particular, glycoside hydrolase family 7 (GH7) CBHs are critically important for the bioeconomy and typically difficult to engineer. Here, we target the discovery of highly active natural GH7 CBHs and engineering of variants with improved activity. Using experimentally assayed activities of genome mined CBHs, we applied sequence and structural alignments to top performers to identify key point mutations linked to improved activity. From ∼1500 known GH7 sequences, an evolutionarily diverse subset of 57 GH7 CBH genes was expressed in Trichoderma reesei and screened using a multiplexed activity screening assay. Ten catalytically enhanced natural variants were identified, produced, purified, and tested for efficacy using industrially relevant conditions and substrates. Three key amino acids in CBHs with performance comparable or superior to Penicillium funiculosum Cel7A were identified and combinatorially engineered into P. funiculosum cel7a, expressed in T. reesei, and assayed on lignocellulosic biomass. The top performer generated using this combined approach of natural diversity genome mining, experimental assays, and computational modeling produced a 41% increase in conversion extent over native P. funiculosum Cel7A, a 55% increase over the current industrial standard T. reesei Cel7A, and 10% improvement over Aspergillus oryzae Cel7C, the best natural GH7 CBH previously identified in our laboratory.

Engineering Enzymes for Environmental Sustainability

The development and implementation of sustainable catalytic technologies is key to delivering our net-zero targets. Here we review how engineered enzymes, with a focus on those developed using directed evolution, can be deployed to improve the sustainability of numerous processes and help to conserve our environment. Efficient and robust biocatalysts have been engineered to capture carbon dioxide (CO2) and have been embedded into new efficient metabolic CO2 fixation pathways. Enzymes have been refined for bioremediation, enhancing their ability to degrade toxic and harmful pollutants. Biocatalytic recycling is gaining momentum, with engineered cutinases and PETases developed for the depolymerization of the abundant plastic, polyethylene terephthalate (PET). Finally, biocatalytic approaches for accessing petroleum-based feedstocks and chemicals are expanding, using optimized enzymes to convert plant biomass into biofuels or other high value products. Through these examples, we hope to illustrate how enzyme engineering and biocatalysis can contribute to the development of cleaner and more efficient chemical industry.

Engineering Enzymes for Environmental Sustainability

The development and implementation of sustainable catalytic technologies is key to delivering our net-zero targets. Here we review how engineered enzymes, with a focus on those developed using directed evolution, can be deployed to improve the sustainability of numerous processes and help to conserve our environment. Efficient and robust biocatalysts have been engineered to capture carbon dioxide (CO2 ) and have been embedded into new efficient metabolic CO2 fixation pathways. Enzymes have been refined for bioremediation, enhancing their ability to degrade toxic and harmful pollutants. Biocatalytic recycling is gaining momentum, with engineered cutinases and PETases developed for the depolymerization of the abundant plastic, polyethylene terephthalate (PET). Finally, biocatalytic approaches for accessing petroleum-based feedstocks and chemicals are expanding, using optimized enzymes to convert plant biomass into biofuels or other high value products. Through these examples, we hope to illustrate how enzyme engineering and biocatalysis can contribute to the development of cleaner and more efficient chemical industry.

Embracing the future of circular bio-enabled economy: unveiling the prospects of microbial fuel cells in achieving true sustainable energy

Sustainable development and energy security, highlighted by the United Nations Sustainable Development Goals (SDGs), necessitate the use of renewable and sustainable energy sources. However, upon careful evaluation of literature, we have discovered that many existing and emerging renewable energy systems (RESs) prioritize renewability over true sustainability. These systems not only suffer from performance inconsistencies and lack of scalability but also fall short in fully embodying the principles of sustainability and circular economy. To address this gap, we propose considering microbial fuel cells (MFCs) as a viable alternative and integral part of the renewable energy ecosystem. MFCs harness the omnipresence, abundance, and cost-effectiveness of their essential components, making them a promising candidate. Through our comprehensive analysis, we shed light on the limitations and advancements of this technology, which underscore the remarkable potential of MFCs to revolutionize our perception of clean, sustainable energy.

Significance of glycans in cellulolytic enzymes for lignocellulosic biorefinery - A review

Lignocellulosic (LC) biomass is the most abundant renewable resource for mankind gravitating society towards sustainable solution for energy that can reduce the carbon footprint. The economic feasibility of 'biomass biorefinery' depends upon the efficiency cellulolytic enzymes which is the main crux. Its high production cost and low efficiencies are the major limitations, that need to be resolved. As the complexity of the genome increases, so does the complexity of the proteome, further facilitated by protein post-translational modifications (PTMs). Glycosylation is regarded the major PTMs and hardly any recent work is focused on importance of glycosylation in cellulase. By modifying protein side chains and glycans, superior cellulases with improved stability and efficiency can be obtained. Functional proteomics relies heavily on PTMs because they regulate activity, localization, and interactions with protein, lipid, nucleic acid, and cofactor molecules. O- and N- glycosylation in cellulases influences its characteristics adding positive attributes to the enzymes.

Recent Advances in β-Glucosidase Sequence and Structure Engineering: A Brief Review

β-glucosidases (BGLs) play a crucial role in the degradation of lignocellulosic biomass as well as in industrial applications such as pharmaceuticals, foods, and flavors. However, the application of BGLs has been largely hindered by issues such as low enzyme activity, product inhibition, low stability, etc. Many approaches have been developed to engineer BGLs to improve these enzymatic characteristics to facilitate industrial production. In this article, we review the recent advances in BGL engineering in the field, including the efforts from our laboratory. We summarize and discuss the BGL engineering studies according to the targeted functions as well as the specific strategies used for BGL engineering.

Genomic analysis of Paenibacillus macerans strain I6, which can effectively saccharify oil palm empty fruit bunches under nutrient-free conditions

The improper disposal of palm oil industrial waste has led to serious environmental pollution. In this study, we isolated Paenibacillus macerans strain I6, which can degrade oil palm empty fruit bunches generated by the palm oil industry in nutrient-free water, from bovine manure biocompost and sequenced its genome on PacBio RSII and Illumina NovaSeq 6000 platforms. We obtained 7.11 Mbp of genomic sequences with 52.9% GC content from strain I6. Strain I6 was phylogenetically closely related to P. macerans strains DSM24746 and DSM24 and was positioned close to the head of the branch containing strains I6, DSM24746, and DSM24 in the phylogenetic tree. We used the RAST (rapid annotation using subsystem technology) server to annotate the strain I6 genome and discovered genes related to biological saccharification; 496 genes were related to carbohydrate metabolism and 306 genes were related to amino acids and derivatives. Among them were carbohydrate-active enzymes (CAZymes), including 212 glycoside hydrolases. Up to 23.6% of the oil palm empty fruit bunches was degraded by strain I6 under anaerobic and nutrient-free conditions. Evaluation of the enzymatic activity of extracellular fractions of strain I6 showed that amylase and xylanase activity was highest when xylan was the carbon source. The high enzyme activity and the diversity in the associated genes may contribute to the efficient degradation of oil palm empty fruit bunches by strain I6. Our results indicate the potential utility of P. macerans strain I6 for lignocellulosic biomass degradation.