Acetoin (AC) is a volatile platform compound with various potential industrial applications. AC contains two stereoisomeric forms: (3)-AC and (3)-AC. Optically pure AC is an important potential intermediate and widely used as a precursor to synthesize novel optically active materials. In this study, chiral (3)-AC production from -2,3-butanediol (-2,3-BD) was obtained using recombinant cells co-expressing-2,3-butanediol dehydrogenase (-2,3-BDH), NADH oxidase (NOX), and hemoglobin protein (VHB) from sp. T241,, and , respectively. The new biocatalyst of/pET--- was developed and the bioconversion conditions were optimized. Under the optimal conditions, 86.74 g/l of (3)-AC with the productivity of 3.61 g/l/h and the stereoisomeric purity of 97.89% was achieved from 93.73 g/l -2,3-BD using the whole-cell biocatalyst. The yield and productivity were new records for (3)-AC production. The results exhibit the industrial potential for (3)-AC production via whole-cell biocatalysis.

(3S)-Acetoin and (2S,3S)-2,3-butanediol are important platform chemicals widely applied in the asymmetric synthesis of valuable chiral chemicals. However, their production by fermentative methods is difficult to perform. This study aimed to develop a whole-cell biocatalysis strategy for the production of (3S)-acetoin and (2S,3S)-2,3-butanediol from meso-2,3-butanediol. First, E. coli co-expressing (2R,3R)-2,3-butanediol dehydrogenase, NADH oxidase and Vitreoscilla hemoglobin was developed for (3S)-acetoin production from meso-2,3-butanediol. Maximum (3S)-acetoin concentration of 72.38 g/L with the stereoisomeric purity of 94.65% was achieved at 24 h under optimal conditions. Subsequently, we developed another biocatalyst co-expressing (2S,3S)-2,3-butanediol dehydrogenase and formate dehydrogenase for (2S,3S)-2,3-butanediol production from (3S)-acetoin. Synchronous catalysis together with two biocatalysts afforded 38.41 g/L of (2S,3S)-butanediol with stereoisomeric purity of 98.03% from 40 g/L meso-2,3-butanediol. These results exhibited the potential for (3S)-acetoin and (2S,3S)-butanediol production from meso-2,3-butanediol as a substrate via whole-cell biocatalysis.

The activities of xylanase extracted from spent mushroom composts (SMCs) of Coprinus comatus, Auricularia auricular, Pleurotus ostreatus, Pleurotus citrinopileatus, Agrocybe cylindracea, Hericium erinaceus, Hypsizygus marmoreus, and Tremella fuciformis were investigated. The crude extract from T. fuciformis SMC showed high xylanase activity with a value of 255.2 U/mg. Furthermore, this xylanase was purified using a combination of ammonium sulfate precipitation, diethylaminoethylcellulose (DEAE-cellulose), and gel filtration column chromatography. The enzyme was purified 20.7-fold with a yield of 43.1% and activity of 5293.8 U/mg. The purified xylanase showed maximum activity at 50 °C and pH 6, retained 80% activity after 1 h incubation at 50 °C, and sustained stability over a wide range of pH values (2 to 10). Under the optimal conditions, the enzyme exhibited a Km value of 2.5 mg/mL towards birchwood xylan. The activity of xylanase was enhanced in the presence of Mg 2+ , Ca 2+ , Ba 2+ , NH4 + , and Tween 80, while some metal ions, particularly Fe 3+ , inhibited its activity. The saccharification of several biomass wastes using the crude xylanase enzyme was studied. The results showed the potential for saccharification of alkaline-pretreated wheat bran solution where 75% saccharification was achieved.

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