Surfactant-assisted ethylenediamine for the deconstruction and conversion of corn stover biomass

Harnessing native nitrogen in lignocellulosic biomass for cellulosic ethanol production by ancestral xylose isomerase-engineered Saccharomyces cerevisiae

Efficient xylose-utilizing Saccharomyces cerevisiae, straightforward pretreatment, elimination of detoxification steps, reduced cellulase dosage, and cost-effective nutrients are critical for the commercialization of lignocellulosic ethanol production. In this study, three highly efficient xylose-utilizing S. cerevisiae, which were capable of consuming 40 g/L xylose within 14 h and consuming a mixture of 80 g/L glucose and 40 g/L xylose within 18 h, were developed by integrating artificial ancestral xylose isomerases into diploid S. cerevisiae genome, followed by laboratory evolution and colony screening. Thereafter, a practical lignocellulosic ethanol process was established, which incorporated DLC(sa) pretreatment (densifying lignocellulosic biomass using sulfuric acid as the reagent), a low cellulase dosage of 14.81 FPU per gram of cellulose, and the elimination of washing or detoxification steps, as well as the need for additional nitrogen sources. Using this approach, 54.8 g/L ethanol was produced from 30 wt% hydrolysate prepared from unwashed corn stover. Further analysis revealed that S. cerevisiae utilized the native nitrogen sources present in the hydrolysate for cell growth and metabolism. In summary, this study offers a practical framework and valuable insights for advancing the commercial production of lignocellulosic ethanol.

Critical analysis of process parameters towards smart bioreactors development in biorefinery for biorenewables production

The development of sustainable biotechnological processes is important for advancements in production of renewable chemicals, biofuels, and materials. A significant challenge is handling high biomass total solids (TS) loading, which is significant to enhance the cost-effectiveness and efficiency of biorefineries. Further, advancements in biomass pretreatment methods, such as hydrodynamic cavitation, that are employed to disrupt the complex structure of biomass, facilitating enzymatic hydrolysis and improving overall process yields, have shown promising results. Efficient pretreatment, novel enzyme evolution and hydrolysis using high TS concentration coupled with process intensification approaches i.e. simultaneous saccharification and co-fermentation (SSCF), simultaneous saccharification and fermentation (SSF), and consolidated bioprocessing (CBP) could be revolutionary in the biomass refineries. There are some key factors influencing reactor performance, such as biomass characteristics, mass transfer, enzyme characteristics, rheology, and heat transfer. These factors are critical in overcoming the challenges associated with high TS loading, including increased viscosity, microorganism selection and reduced mixing efficiency. This review highlights such critical factors when dealing with high biomass loading, by presenting strategies and reactor configurations to improve the scalability and economic viability of lignocellulosic biorefineries.

Enhancing enzymatic conversion of castor stalk through dual-functional ethanolamine pretreatment

Castor stalk from hemp plants is an attractive lignocellulosic feedstock for biomass refining valorization due to its similar chemical composition to hardwoods. In this study, the castor stalk fibers were pretreated with efficient dual-functional ethanolamine to achieve delignification and swelling of the cellulosic fibers, followed by cellulase enzymatic digestion for biomass conversion. Experimental results showed that ethanolamine pretreatment at 160 °C for 1 h effectively removed 69.20 % of lignin and 43.18 % of hemicellulose. In addition to efficient delignification and removal of hemicellulose, the study also revealed that supramolecular structure of cellulose was another major factor affecting enzymatic hydrolysis performance. The lowered crystallinity (60-70 %) and swelled crystal sizes (2.95-3.04 nm) promoted enzymatic hydrolysis efficiency during the heterogeneous reaction process. Under optimal conditions (160 °C, 1 h; enzyme loading: 15 FPU/g substrate), promoted yields of 100 % glucose and over 90 % xylose were achieved, which were significantly higher than those obtained from untreated castor stalk. These findings highlighted the effectiveness of the dual-functional ethanolamine pretreatment strategy for efficient bioconversion of lignocellulosic feedstocks. Overall, this study provides valuable insights into the development of new strategies for the efficient utilization of biomass resources, which is essential for the sustainable development of our society.

Bioconversion of spray corn husks into L-lactic acid with liquid hot water pretreatment

Agricultural by-products like rice husk, bran, and spray corn husks, often utilized as feed, are considered less desirable. This study aims to enhance the utilization rate of these materials by subjecting then to liquid hot water (LHW) pretreatment, followed by enzymatic hydrolysis to produce fermentable sugars. We investigated the production of L-lactic acid using two methods: simultaneous saccharification fermentation (SSF) and separate hydrolysis fermentation (SHF), following varying intensities of LHW pretreatment. The results showed that the optimal enzymatic hydrolysis efficiency was achieved from spray corn husks under the pretreatment conditions of 155 °C and 15 min. SHF was generally more effective than SSF. The glucose L-lactic acid conversion rate in SHF using spray corn husks can reach more than 90 %. Overall, this work proposed a novel, environmental-friendly strategy for efficient and for L- lactic acid production from spray corn husks.

Enzymolysis kinetics of corn straw by impeded Michaelis model and Box-Behnken design

Enzymatic hydrolysis is an essential step in the lignocellulosic biorefining process. In this paper, Box-Behnken was used to optimize the enzymatic hydrolysis process of corn stalk, and the promotion effect of three typical surfactants on the enzymatic hydrolysis process was investigated. The experimental results showed that the total reducing sugar yield reached 67.6% under the best-predicted conditions. When the concentration of Tween 80 is 0.1%, it could be increased to 80.2%. In addition, the Impeded Michaels Model (IMM) is introduced in this study to describe the enzymatic hydrolysis process of corn stalks. Finally, the initial contact coefficient between the enzyme and cellulose (Kobs,0) and the gradual loss coefficient of enzyme activity (ki) caused by reaction obstruction were obtained by fitting data, which successfully verified the rationality of the model.

Surfactant-assisted dilute ethylenediamine fractionation of corn stover for technical lignin valorization and biobutanol production

In this study, a surfactant-assisted diluted ethylenediamine (EDA) fractionation process was investigated for co-generation of technical lignin and biobutanol from corn stover. The results showed that the addition of PEG 8000 significantly enhanced cellulose recovery (88.9 %) and lignin removal (68.9 %) in the solid fraction. Moreover, the pulp achieved 86.5 % glucose yield and 82.6 % xylose yield in enzymatic hydrolysis. Structural characterization confirmed that the fractionation process promoted the preservation of active β-O-4 bonds (35.8/100R) in isolated lignin and functionalized the lignin through structural modification using EDA and surfactant grafting. The enzymatic hydrolysate of the pulps yielded a sugar solution for acetone-butanol-ethanol (ABE) fermentation, resulting in an ABE concentration of 15.4 g/L and an overall yield of 137.2 g/Kg of dried corn stalk. Thus, the surfactant-assisted diluted EDA fractionation has the potential to enhance the overall economic feasibility of second-generation biofuels production within the framework of biorefinery.