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CuAsp with a fiber-like structure exhibited both NADH peroxidase- and glycerol dehydrogenase (GlyDH)-mimetic activities.

Microbial contamination is a serious challenge that needs to be overcome for the successful biosynthesis of 2,3-butanediol (2,3-BD). However, traditional strategies such as antibiotic administration or sterilization are costly, have high energy demands, and may increase the risk of antibiotic resistance. Here, we intend to develop a robust strategy to achieve non-sterilized fermentation of 2,3-BD. Briefly, the robust strain can metabolize unconventional chemicals as essential growth nutrients, and therefore, outcompete contaminant microbes that cannot use unconventional chemicals. To this end, Klebsiella pneumoniae OU7, a robust strain, was confirmed to rapidly exploit urea and phosphite (unconventional chemicals) as the primary sources of nitrogen (N) and phosphorus (P), and withstand deliberate contamination in the possibly contaminated systems. Secondly, metabolic engineering, pathogenicity elimination and adaptive laboratory evolution were successively performed, endowing the best strain with an excellent fermentation performance for safe 2,3-BD production. Finally, 84.53 g L−1 of 2,3-BD was synthesized with a productivity of 1.17 g L−1 h−1 and a yield of 0.38 g g−1 under the non-sterilized system. In summary, our technique reduces labor and energy costs and simplifies the fermentation process because sterilization does not need to be performed. Thus, our work will be beneficial for the sustainable synthesis of 2,3-BD.

Different kinds of low transition temperature mixtures (LTTMs) were synthesized with DL-lactic acid and five different quaternary ammonium salts respectively, and their viscosity and solubility parameters change with different molar ratios of quaternary ammonium salt to DL-lactic acid were investigated and compared with anthocyanins. Then the LTTMs synthesized were used to extract anthocyanins from saskatoon berry (Amelanchier alnifolia Nutt.). It turned out that the choline chloride/DL-lactic acid (ChCl/LA) showed the best solubility of anthocyanins compared with the other LTTMs, which was in line with solubility parameter theory. Under the optimized process condition with 1 : 15 of molar ratio, 1 : 20 of solid to liquid ratio, 50 °C of extraction temperature and 45 min of extraction time, the extraction amount of anthocyanins reached 525.27 ± 0.82 mg per 100 g and the extracted rate of anthocyanins was 87.4%. Then the macroporous resin AB-8 adsorbent was used to separate and purify the anthocyanin compounds from saskatoon berry, with a recovery yield of 65.7%. Further, the confirmation of the purified anthocyanins was carried out using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and high performance liquid chromatography-mass spectrometry (HPLC-MS). Finally, the purified anthocyanins were proved to be good antioxidants through the comparison with vitamin C and butylated hydroxytoluene.

As novel low-viscosity and environmentally-friendly reaction media, deep eutectic solvents (DESs) have gained much attraction in biocatalysis. In this study, various DESs were prepared and their effects on the asymmetric oxidation of racemic 1-(4-methoxyphenyl)ethanol (MOPE) catalyzed by Acetobacter sp. CCTCC M209061 cells to give enantiopure (S)-MOPE were examined. The best results were obtained with the DES [ChCl][Gly] and its concentration exerted a significant influence on the reaction, with the optimal content being 10% (v/v). In the [ChCl][Gly]-containing system, the substrate concentration was substantially increased (55 mmol L−1 vs. 30 mmol L−1) as compared with the [ChCl][Gly]-free aqueous system, while the residual substrate e.e. was kept as high as 99.9%. The good biocompatibility of [ChCl][Gly] with the cells and the improved cell membrane permeability in the [ChCl][Gly]-containing system could partly account for the clearly enhanced reaction efficiency.

Aqueous ionic liquid (IL) solutions have recently received significant interest as promising alternatives to neat ILs for lignocellulose pretreatment because of many advantages. In this study, 39 aqueous cholinium IL solutions were used to pretreat rice straw for improving the subsequent enzymatic saccharification. Strong correlations were observed between the pH of these aqueous ILs and their respective delignification capacities, between their pH and the polysaccharide digestibility, and between their pH and the corresponding reducing sugar yields. More than 55% of the lignin was removed from rice straw after pretreatment with aqueous ILs of pH > 11.0, thus resulting in a high digestibility (88–96% for cellulose and 65–89% for xylan) during the process of enzymatic saccharification. Establishing this type of correlation between the pH of aqueous ILs and their pretreatment effectiveness may be useful for the rational design and selection of ILs for lignocellulosic biomass pretreatment.

Seven ionic liquids (ILs) were tested for use in the regioselective acylation of 1-β-D-arabinofuranosylcytosine (ara-C) by vinyl propionate, catalyzed by immobilized Candida antarctica lipase B. The results demonstrated that the nature of both the cations and the anions of ILs had a significant effect on the initial rate and the substrate conversion, but little effect on the regioselectivity of the reaction. The lipase displayed enhanced activity toward ara-C when the alkyl chain of CnMIm·BF4 increased in length (n = 4–8) and no acylation reaction occurred in C4MIm·Cl or C4MIm·Br. To further enhance the initial rate and substrate conversion, co-solvent mixtures of ILs and organic solvents were investigated. Among various IL-containing systems examined, 10% (v/v) C4MIm·PF6–tetrahydrofuran gave the highest initial rate and substrate conversion. In this reaction medium, the optimal water activity, vinyl propionate/ara-C molar ratio, temperature and shaking rate were 0.07, 15 ∶ 1 (mol/mol), 60 °C and 250 rpm, respectively. Under these conditions, the initial rate, substrate conversion and the regioselectivity were 94.0 mM h−1, 98.5% and 99%, respectively. An additional comparative study demonstrated that the enzymatic acylation proceeded with very similar initial rate, substrate conversion, regioselectivity and activation energy whether the reaction medium was 10% (v/v) C4MIm·PF6–tetrahydrofuran or 28% (v/v) hexane–pyridine (the best organic solvent mixture for the reaction). However, the lipase exhibited a much higher stability in the IL-containing system, which may also have environmental advantages. The product of the lipase-catalysed reaction was characterized by NMR, FT-IR spectroscopy and was shown to be the 5′-O-monoester of ara-C.

Ionic liquids (ILs) containing a range of 1-alkyl-3-methylimidazolium cations and various anions affect papain's catalytic performance and thermostability in a manner that correlates closely with the effects of the ILs on the conformation of the enzyme as assessed by using ATR-FTIR and fluorescence techniques.

The biocatalytic anti-Prelog enantioselective reduction of 4′-methoxyacetophenone (MOAP) to (R)-1-(4-methoxyphenyl)ethanol {(R)-MOPE} using immobilized Trigonopsis variabilis AS2.1611 cells was, for the first time, successfully conducted in an ionic liquid (IL)-containing system. Of all the tested ILs, the best results were observed in the co-solvent system containing 1-(2′-hydroxyl)ethyl-3-methylimidazolium nitrate (C2OHMIM·NO3), which showed the good biocompatibility with the cells and only a moderate increase in the cell membrane permeability. It was found that the optimal content of C2OHMIM·NO3, buffer pH, reaction temperature, substrate concentration and shaking rate were 2.5% (v/v), 8.5, 30 °C, 15 mM and 200 r min−1, respectively. Under these optimized conditions, the initial reaction rate, the maximum yield and the product e.e. were 7.1 μmol h−1, 97.2% and >99%, respectively, which are much higher than the corresponding values previously reported. The presence of C2OHMIM·NO3 in aqueous buffer allowed the cells to tolerate relatively high temperatures and substrate concentrations compared with those in aqueous buffer without IL. Additionally, the immobilized cells manifested excellent operational and storage stability. Hence, the whole-cell biocatalytic anti-Prelog reduction of MOAP to (R)-MOPE on a preparative scale in the presence of C2OHMIM·NO3 appears to be a promising and competitive reaction

Novel solid acid catalysts for esterification have recently been described that are made by incomplete carbonization of carbohydrates followed by sulfonation. Herein, such a ‘sugar catalyst’ is prepared from D-glucose and its catalytic properties and structure are investigated in detail. This type of sugar catalyst is, for the first time, applied for the effective production of biodiesel from waste oils. Our results indicate that sugar catalysts are highly effective, minimally polluting and re-usable catalysts that are highly suited to the production of biodiesel from waste oils with a high acid value.

The two typical ionic liquids (ILs), one hydrophobic (BMIM·PF6) and one hydrophilic (BMIM·BF4), were tested as solvents for use in the asymmetric reduction of acetyltrimethylsilane (ATMS) to enantiopure (S)-1-trimethylsilylethanol {(S)-1-TMSE} catalyzed by immobilized Saccharomyces cerevisiae cells. The results demonstrate that BMIM·PF6 and BMIM·BF4 can markedly boost the activity and the stability of the immobilized cells. To better understand the reaction performed in these IL-containing systems, various variables that influenced the performance of the reaction were examined. The optimal buffer pH, reaction temperature and substrate concentration were 7.3, 30 °C and 84 mM, respectively, for the BMIM·PF6/buffer (1/6, v/v) biphasic system, and 7.5, 30 °C and 77 mM, respectively, for the 10% (v/v) BMIM·BF4–buffer co-solvent system. Under the optimal conditions, the initial reaction rate, maximum yield and product e.e. were 63.4 mM h−1, 99.9% and >99.9% with the former system, while those with the latter system were 74.5 mM h−1, 99.2% and >99.9%, respectively, which were much higher than those achieved with either n-hexane/buffer (2/1, v/v) biphasic system or aqueous buffer. It was also found that the optimal pH and substrate concentration changed when n-hexane was replaced by BMIM·PF6 or BMIM·BF4. Although the optimal reaction temperature remained the same in the four kinds of reaction systems, the temperature profile of the reaction varied from case to case. Additionally, BMIM·BF4 and especially BMIM·PF6 exhibited greater biocompatibility with Saccharomyces cerevisiae than n-hexane, and could be used repeatedly for economically interesting whole-cell biocatalytic processes with in situ coenzyme regeneration.