High bioethanol titer and yield from phosphoric acid plus hydrogen peroxide pretreated paper mulberry wood through optimization of simultaneous saccharification and fermentation

Advancements in lignocellulosic biorefining: An integrated approach for achieving complete conversion of unsterilized peanut shells into high-titer ethanol and succinic acid

The inefficient utilization of carbon sources poses a critical bottleneck in lignocellulose biorefinery processes. This study aimed to devise an integrated approach for efficiently releasing the fermentable sugars from pretreated peanut shells, and subsequently converting the hexoses and pentoses into ethanol and succinic acid (SA), while minimizing carbon dioxide emissions. An enhanced cellulolytic enzyme catalytic system (CECS) has been developed through the optimization of accessory enzymes and additives. This system synergistically boosted both the thermal stability and catalytic activity of the cellulase, and enhanced the glucose yield by 15.95 % at a substrate loading of 10 % (w/v). The implementation of a fed-batch strategy improved the efficiency of high-solids (25 % w/v) enzymatic hydrolysis, when it was integrated with the developed CECS, a remarkable glucose yield of up to 79.40 % was achieved. The semi-simultaneous saccharification, in conjunction with a step-wise fermentation process, enabled the efficient conversion of pentoses and hexoses from pretreated peanut shells into high titers of ethanol (83.13 g/L) and SA (45.21 g/L) under non-sterilized conditions. This approach achieved conversion rates of up to 41.10 g ethanol and 100.57 g SA per kilogram of peanut shells raw material, while effectively mitigating carbon dioxide emissions during the process.

Fermentation of Biomass and Residues from Brazilian Agriculture for 2G Bioethanol Production

Brazil is one of the world's leading producers of staple foods and bioethanol. Lignocellulosic residual sources have been proposed as a promising feedstock for 2G bioethanol and to reduce competition between food and fuels. This work aims to discuss residual biomass from Brazilian agriculture as lignocellulosic feedstock for 2G bioethanol production as bagasse, stalk, stem, and peels, using biorefining concepts to increase ethanol yields. Herein, we focused on biomass chemical characteristics, pretreatment, microorganisms, and optimization of process parameters that define ethanol yields for bench-scale fermentation. Although several techniques, such as carbon capture, linking enzymes to supports, and a consortium of microorganisms, emerge as future alternatives in bioethanol synthesis, these technologies entail necessary optimization efforts before commercial availability. Overcoming these challenges is essential to linking technological innovation to synthesizing environmentally friendly fuels and searching other biomass wastes for 2G bioethanol to increase the biofuel industry's potential. Thus, this work is the first to discuss underutilized lignocellulosic feedstock from other agrifoods beyond sugar cane or corn, such as babassu, tobacco, cassava, orange, cotton, soybean, potatoes, and rice. Residual biomasses combined with optimized pretreatment and mixed fermentation increase hydrolysis efficiency, fermentation, and purification. Therefore, more than a product with a high added value, bioethanol synthesis from Brazilian residual biomass prevents waste production.

Enhancing simultaneous saccharification and co-fermentation of corncob by Kluyveromyces marxianus through overexpression of putative transcription regulator

Overexpression of a gene with unknown function in Kluyveromyces marxianus markedly improved tolerance to lignocellulosic biomass-derived inhibitors. This overexpression also enhanced tolerance to elevated temperatures, ethanol, and high concentrations of NaCl and glucose. Inhibitor degradation and transcriptome analyses related this K. marxianusMultiple Stress Resistance (KmMSR) gene to the robustness of yeast cells. Nuclear localization and DNA-binding domain analyses indicate that KmMsr is a putative transcriptional regulator. Overexpression of a mutant protein with deletion in the flexible region between amino acids 100 and 150 further enhanced tolerance to multiple inhibitors during fermentation, with ethanol production and productivity increasing by 36.31 % and 80.22 %, respectively. In simultaneous saccharification co-fermentation of corncob without detoxification, expression of KmMSR with the deleted flexible region improved ethanol production by 5-fold at 42 °C and 2-fold at 37 °C. Overexpression of the KmMSR mutant provides a strategy for constructing robust lignocellulosic biomass using strains.