An efficient and eco-friendly approach for the sustainable recovery and properties characterization of polyhydroxyalkanoates produced by methanotrophs.

Synthetic biodegradable and bio-based polymers have emerged as sustainable alternatives to nonrenewable petroleum-derived polymers which cause serious environmental issues. In particular, polyhydroxyalkanoates (PHA) are promising biopolymers owing to their outstanding biodegradability and biocompatibility. The production of the homopolymer poly(3-hydroxybutyrate) (PHB) and copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from type II methanotrophs via microbial fermentation was presented. For the efficient extraction and recovery of intracellular PHA from methanotrophs, different extraction approaches were investigated including solvent extraction using 1,3-dioxolane as a green solvent, integrated cell lysis and solvent extraction, and cell digestion without the use of organic solvents. Among various extraction approaches, the integrated method exhibited the highest extraction performance, with PHA recovery and purity exceeding 91 % and 93 %, respectively, even when the PHA content of the cells was low. Furthermore, the molecular weight, thermal stability, and mechanical properties of the recovered PHA were comprehensively analyzed to suggest its suitable practical applications. The obtained properties were comparable to that of the commercial PHA products and PHA produced from other microbial species, indicating an efficient recovery of high-quality PHA produced from methanotrophs.

Sustainable biopolyol production via solvothermal liquefaction silvergrass saccharification residue: Experimental, economic, and environmental approach.

With the rising environmental concern, sustainable chemistry should be accomplished by considering technical, economic, and environmental factors that guarantee the successful implementation of new alternative products. Hence, we performed the integrated techno-economic and life cycle assessment for two-step solvothermal liquefaction (two-pot synthesis) and simplified solvothermal liquefaction (one-pot synthesis) based on experiment results. Based on the itemized cost estimation, the unit biopolyol production costs obtained from the two-pot synthesis and one-pot synthesis were 10.0 $ kg-1 and 2.89 $ kg-1, respectively. To provide techno-economic guidelines for biopolyol production, profitability analysis, and uncertainty analysis were used to identify the economic feasibility of the proposed processes. In addition, the life cycle assessment results indicated that biopolyol production via the two-pot synthesis leads to a slightly lower greenhouse gas emission compared with the one-pot synthesis, which further required the use of an analytic hierarchy process to determine the best process for biopolyol production depending on the different weight points in the economic and environmental aspects. From these results, we can provide the technical performance, economic feasibility, and environmental impact of lab-scale biopolyol production from silvergrass residue, a low-cost waste of biomass saccharification.

Catalytic hydrogenolysis of alkali lignin in supercritical ethanol over copper monometallic catalyst supported on a chromium-based metal-organic framework for the efficient production of aromatic monomers.

The catalytic hydrogenolysis of lignin has been reported as an effective approach for lignin depolymerization owing to its high efficiency for aromatic monomer production. In this study, a series of copper monometallic catalysts over an MIL-101(Cr) support were synthesized and used for the catalytic hydrogenolysis of alkali lignin using supercritical ethanol. First, the optimal copper catalyst for lignin hydrogenolysis was selected. Subsequently, the reaction conditions for catalytic hydrogenolysis were systematically optimized to maximize the total monomer yield. The optimal conditions were determined to be 6 h of reaction time, 20 min of sonication pretreatment, 50% catalyst loading, and 5% lignin loading. Under these conditions, an aromatic monomer yield of 38.5% was obtained; this depolymerized lignin stream, which is mainly composed of G-type monomers, can serve as a promising aromatic feedstock and carbon source for further microbial upgrading and bioconversion to produce various value-added products.

Co-upgrading of ethanol-assisted depolymerized lignin: A new biological lignin valorization approach for the production of protocatechuic acid and polyhydroxyalkanoic acid.

This study presents a promising biological co-upgrading of ethanol-assisted depolymerized lignin (EDL) into protocatechuic acid (PCA) and polyhydroxyalkanoic acid (PHA) without any separation process. A depolymerized alkali lignin containing various G-lignin-type monomers at a concentration of 77 mg/mL was used for co-upgrading. An engineered Pseudomonas putida KT2440 strain was constructed by knocking out the protocatechuate 3, 4-dioxygenase, expression of the formaldehyde utilization pathway, and the expression of aldehyde dehydrogenase to enhance the efficiency of the ethanol utilization pathway. The growth and production of value-added bioproducts have been promoted by the utilization of formaldehyde, resulted in 6.73 ± 0.26 mg/L of PCA with a 17.5% (w/w) yield of total lignin monomers, and 303.66 ± 26.75 mg/L of PHA with 21.26% (w/w) of dry cell weight from 0.5 mL EDL. Moreover, the ethanol solvent used for lignin depolymerization was also utilized along with depolymerized lignin for co-upgrading to value-added products.

Microwave-Assisted Two-Step Liquefaction of Acetone-Soluble Lignin of Silvergrass Saccharification Residue for Production of Biopolyol and Biopolyurethane.

The application of microwave heating facilitated efficient two-step liquefaction of acetone-soluble lignin obtained from saccharification residue of Miscanthus sacchariflorus (silvergrass), which was prepared by enzymatic hydrolysis, to produce biopolyol with a low acid number and favorable hydroxyl number. The acetone-soluble lignin was liquefied using a crude glycerol and 1,4-butanediol solvent mixture at various solvent blending ratios, biomass loadings, acid loadings, and reaction temperatures. The optimal reaction condition was determined at a solvent blending ratio of crude glycerol to 1,4-butanediol of 1:2, 20% of biomass loading, and 1% of catalyst loading at a reaction temperature of 140 °C for 10 min. Subsequently, the optimal biopolyol was directly used for the preparation of biopolyurethane foam as a value-added product. The chemical and physical properties of biopolyurethane foams derived from acetone-soluble lignin were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and high-resolution scanning electron microscopy (HR-SEM). In addition, mechanical properties of produced biopolyurethane foams, including compressive strength and density, were also characterized to suggest their appropriate applications. The results indicated that the biopolyurethane foam can be used as a green replacement for petroleum-based polyurethane foam due to its comparable thermal properties, mechanical strength, and morphological structure.