Development of bioprocess for corncob-derived levulinic acid production

Alcoholysis of High-Solid xylose residue for methyl levulinate preparation and its kinetics

Achieving the efficient biomass alcoholysis to methyl levulinate (ML) under high solid content conditions and establishing its kinetic model are crucial, but remain challenging. Here, the alcoholysis of microcrystalline cellulose (MC) and xylose residue (XR) to ML under high solid content conditions using CuSO4 as a catalyst was reported. High yield (34.96 wt%) and concentration (41.48 g/L) of ML from MC alcoholysis are achieved under the optimal conditions. Meanwhile, the yield and concentration of ML from XR alcoholysis can reach 26.73 wt% and 31.72 g/L, respectively. The alcoholysis pathways of MC and XR are proposed. A mixed model consisting of a shrinking core model and a pseudo-first-order kinetic model was established to elucidate the alcoholysis behavior of biomass. The generation of glucose is the rate-limiting step of the alcoholysis process, and there is no significant dependence between the activation energies of main reactions and the solid content of biomass.

Bio-mitigation of CO2: The co-production of phycocyanin and optically pure (R)-γ-valerolactone with perfect enantiomeric excess

To overcome the climate crisis, various greenhouse gas (GHG) mitigation strategies have been developed, and every effort has been made to achieve carbon neutrality. Given that petroleum-based industries and the transportation sector emit enormous amounts of GHGs, the product spectra of biorefineries should be expanded beyond drop-in biofuels to include more value-added products. This study aimed to construct a CO2 mitigation system. When CO2 was used as the sole feedstock, value-added phycocyanin and enantioselective γ-valerolactone (GVL) were produced as follows (i) Galdieria sulphuraria was phototrophically cultured to produce phycocyanin (ii) the residual G. sulphuraria after phycocyanin extraction was used as the feedstock for producing levulinic acid and formic acid and (iii) the engineered hydroxybutyrate dehydrogenase-based chemo-enzymatic reaction converted levulinic acid to (R)-GVL with perfect enantiomeric excess > 99.999 %. The results not only contribute to broadening the product spectrum of CO2 biorefineries but also provide strategies to achieve carbon neutrality.

Synergistically Enhanced Co-Adsorption of Reactant and Hydroxyl on Platinum-Modified Copper Oxide for High-Performance HMF Oxidation

Electrochemical oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) provides an environmentally friendly route for producing the sustainable polymer monomer 2,5-furandicarboxylic acid (FDCA). Thus, precisely adjusting the synergistic adsorption among key reactive species, such as HMF and OHads, on the carefully designed catalyst surface is essential for achieving satisfactory catalytic performance for HMF oxidation to FDCA as it is closely related to the adsorption strength and configuration of the reaction substrates. This kind of regulation will ultimately facilitate the improvement of HMF oxidation performance. In this work, Pt nanoparticles modified CuO nanowires (denoted as Pt/CuO@CF) are constructed for the selective electrooxidation of HMF to FDCA under alkaline conditions. The well-designed Pt/CuO@CF demonstrates highly impressive catalytic performance across a range of HMF concentrations, ranging from the commonly used concentrations to higher levels typically not explored (10, 25, 50, 75, and 100 mm) with high FEFDCA (all above 95%) and outstanding long-term stability (15 cycles). In situ experimental characterizations confirm that the designed heterogeneous interface between Pt and CuO enhances the enrichment of HMF and OHads species on the catalyst surface. Theoretical calculations reveal the anchored Pt nanoparticles reduce the adsorption barrier for HMF and OHads, thereby promoting the highly selective oxidation of HMF to FDCA.

Biotechnological valorization of levulinic acid as a non-sugar feedstock: New paradigm in biorefineries

Due to the severe climate crisis, biorefineries have been highlighted as replacements for fossil fuel-derived refineries. In traditional sugar-based biorefineries, levulinic acid (LA) is a byproduct. Nonetheless, in 2002, the US Department of Energy noted that LA is a significant building block obtained from biomass, and the biorefinery paradigm has shifted from being sugar-based to non-sugar-based. Accordingly, LA is of interest in this review since it can be converted into useful precursors and ultimately can broaden the product spectrum toward more valuable products (e.g., fuels, plastics, and pharmaceuticals), thereby enabling the construction of economically viable biorefineries. This study comprehensively reviews LA production techniques utilizing various bioresources. Recent progress in enzymatic and microbial routes for LA valorization and the LA-derived product spectrum and its versatility are discussed. Finally, challenges and future outlooks for LA-based non-sugar biorefineries are suggested.

Integrated Preparation of Hollow Lignin Nanoparticles as a Drug Carrier and Levulinic Acid from the Poplar Wood Prehydrolysis Liquor

Prehydrolysis liquid (PHL) from dissolving pulp and biorefinery industries is rich in saccharides and lignin, being considered as a potential source of value-added materials and platform molecules. This study proposed an environmentally friendly and simple method to prepare morphologically controllable hollow lignin nanoparticles (LNPs) and levulinic acid (LA) from PHL. In the first step, after hydrothermal treatment of PHL with p-toluenesulfonic acid (p-TsOH), lignin with a uniform molecular weight was obtained to prepare LNPs. The prepared LNPs have an obvious hollow structure, with an average size of 490-660 nm, and exhibit good stability during 30 days of storage. When the as-obtained LNPs were used as a sustained-release agent for amikacin sulfate, the encapsulation efficiency reached over 70% and the release efficiency within 40 h reached 69.2% in a pH 5.5 buffer. Subsequently, the remaining PHL that contains saccharides was directly used for LA production under the catalysis of p-TsOH. At 150 °C for 1.5 h, the LA yield reached 58.4% and remained at 56% after 5 cycles of p-TsOH. It is worth noting that only p-TsOH was used as a reactive reagent throughout the entire preparation process. Overall, this study provided a novel pathway for the integrated utilization of PHL and showed the immense potential of the preparation and application of LNPs.

Waste to Energy: Steam explosion-based torrefaction process to produce solid biofuel for power generation utilizing various waste biomasses

Currently, humankind is facing a serious environmental and climate crisis, which has accelerated the research on producing bioenergy from waste biomass as a carbon-neutral feedstock. In this study, the aim was to develop an upcycling strategy for waste biomass to solid-type biofuel conversion for power generation. Various types of waste biomass (i.e., waste wood after lumbering, sawdust-type mushroom waste wood, kudzu vine, and empty fruit bunches from palm) were used as sustainable feedstocks for steam explosion-based torrefaction. The reaction conditions were optimized for each waste biomass by controlling the severity index (Ro); the higher heating value increased proportional to the Ro increase. Additionally, component analysis revealed that steam explosion torrefaction mainly degraded hemicellulose, and most of the torrefied waste biomass met the Bio-Solid Refuse Fuel quality standard. The results provide not only a viable waste-to-energy strategy but also insights to address global climate change.

Coupling process for preparing biomass-based furfural and levulinic acid from corncob: Extraction, green chemistry and techno-economic assessment

The purpose of this study is to design and investigate two coupling processes for acid-catalyzed hydrolysis of corncob, achieving the simultaneous preparation of biomass-based furfural and levulinic acid (LA). Meanwhile, high concentration and yield of LA were obtained through a situ feeding strategy of pretreated furfural residue with high solids loading (20%, w/v). In Scenario A, 2-methyltetrahydrofuran was selected as the solvent for the LA extraction process compared with the neutralization process in Scenario B. Techno-economic assessment results show that Scenario A is technically feasible and cost-competitive, with an internal rate of return of 21.92%, a net present value of 121 million US dollars, a carbon efficiency of 72%, an environmental factor of 4.38, and a process mass intensity of 32.19. This study will provide new insights for fully utilizing lignocellulosic biomass to prepare renewable energy resources, comprehensively evaluating the economic feasibility, and promoting green and low-carbon development.

Engineering of Yarrowia lipolytica as a platform strain for producing adipic acid from renewable resource

There is an increasing demand for bio-based dicarboxylic acids (DCA) as an eco-friendly alternatives to chemically synthesized DCA. Adipic acid, which is not naturally produced by microorganisms, is an essential DCA with significant industrial importance. This study aimed to develop a platform strain using Yarrowia lipolytica for efficient bioconversion of renewable resources into adipic acid. To prevent the complete oxidation of adipic acid, peroxisomal β-oxidation was engineered by selectively disrupting acyl-CoA oxidases. Furthermore, ω-oxidation activity was improved via introducing an additional copy of cytochrome P450 monooxygenase (ALK5) and reductase (CPR1) with fatty alcohol oxidase (FAO1). The production phase used SP92D medium in a two-stage bioconversion process, during which the engineered strain exhibited the highest production level, achieving a remarkable 9.7-fold increase compared to that of the parental strain. To our knowledge, this is the first report demonstrating that engineered Y. lipolytica can produce adipic acid from fatty acid methyl esters.