Isolation of a Bacillus cereus strain HBL-AI and its application for production of Trans-4-hydroxy-l-proline

Application of PHA surface binding proteins of alkali-tolerant Bacillus as surfactants

Amphiphilic protein has lipophilic and hydrophilic domains, displaying the potential for development as a biosurfactant. The polyhydroxyalkanoate (PHA) surface binding protein derived from Bacillus is a type of protein that has not been studied for its emulsifying properties. In this study, PHA granule-associated protein (PhaP), PHA regulatory protein (PhaQ), and PHA synthase subunit (PhaR) derived from an alkali-tolerant PHA-producing Bacillus cereus HBL-AI were found and heterologously expressed in E. coli and purified to investigate their application as biosurfactants. It showed that the emulsification ability and stability of three amphiphilic proteins were higher than those of widely used chemical surfactants in diesel oil, vegetable oil, and lubricating oil. In particular, the PhaQ protein studied for the first time can form a stable emulsion layer in vegetable oil at a lower concentration (50 µg/mL), which greatly reduced the amount of protein used in emulsification. This clearly demonstrated that the PHA-binding protein of HBL-AI can be well applied as an environmentally friendly biosurfactants.

Traditional Chinese medicine residue enzymatic hydrolysates for production of polyhydroxyalkanoate by newly isolated Bacillus altitudinis

Traditional Chinese medicine residue (TCMR) was utilized as an inexpensive carbon source for the production of poly(3-hydroxybutyrate) (PHB) using the newly isolated Bacillus altitudinis HBU-SI7. The results showed that Yu Ping Feng TCMR could be directly hydrolysed by cellulase to obtain a high proportion of glucose (99 % of total sugar) without pretreatment, achieving an enzymatic hydrolysis rate of up to 89.2 %. B. altitudinis could grow and produce PHB when using enzymatically hydrolysed TCMR in a 5-L fermenter. After 20 h of fermentation, the maximum concentration of PHB was 11.2 g/L, and the highest cell dry weight (CDW) was 15.4 g/L, with 72.7 % of the PHB fraction in CDW. Moreover, this strain could utilize enzymatic hydrolysates from various herbal formulas to produce high levels of PHB. This novel approach aims to accumulate PHB from TCMR hydrolysates, offering an effective and environmentally friendly method to reduce production costs and achieve mass production.

Characterization and Application of a Novel Glucose Dehydrogenase with Excellent Organic Solvent Tolerance for Cofactor Regeneration in Carbonyl Reduction

An efficient cofactor regeneration system has been developed to provide a hydride source for the preparation of optically pure alcohols by carbonyl reductase-catalyzed asymmetric reduction. This system employed a novel glucose dehydrogenase (BcGDH90) from Bacillus cereus HBL-AI. The gene encoding BcGDH90 was found through the genome-wide functional annotation. Homology-built model study revealed that BcGDH90 was a homo-tetramer, and each subunit was composed of βD-αE-αF-αG-βG motif, which was responsible for substrate binding and tetramer formation. The gene of BcGDH90 was cloned and expressed in Escherichia coli. The recombinant BcGDH90 exhibited maximum activity of 45.3 U/mg at pH 9.0 and 40 °C. BcGDH90 showed high stability in a wide pH range of 4.0-10.0 and was stable after the incubation at 55 °C for 5 h. BcGDH90 was not a metal ion-dependent enzyme, but Zn2+ could seriously inhibit its activity. BcGDH90 displayed excellent tolerance to 90% of acetone, methanol, ethanol, n-propanol, and isopropanol. Furthermore, BcGDH90 was applied to regenerate NADPH for the asymmetric biosynthesis of (S)-(+)-1-phenyl-1,2-ethanediol ((S)-PED) from hydroxyacetophenone (2-HAP) with high concentration, which increased the final efficiency by 59.4%. These results suggest that BcGDH90 is potentially useful for coenzyme regeneration in the biological reduction.