Steroid medication is used extensively in clinical applications and comprises a large and vital part of the pharmaceutical industry. However, the difficulty of separating 4-androstene-3,17-dione （AD） from 1,4-androstadiene- 3,17-dione （ADD） restricts the application of the microbial transformation of phytosterols in the industry. A novel at- mospheric and room temperature plasma （ARTP） treatment, which employs helium as the working gas, was used to generate Mycobacterium neoaurum mutants producing large amounts of AD. After treatment of cultures with ARTP, four mutants were selected using a novel screening method with a color assay. Among the mutants, M. neoaurum ZADF-4 was considered the best candidate for industrial application. When the fermentation medium contained 15 g/L phytosterols and was cultivated on a rotary shaker at 160 r/min at 30 ~C for 7 d, （6.28＋0.11） g/L of AD and （0.82＋0.05） g/L of ADD were produced by the ZADF-4 mutant, compared with （4.83＋0.13） g/L of AD and （2.34＋0.06） g/L of ADD by the original strain, Iv~. neoaururn ZAD. Compared with ZAD, the molar yield of AD increased from 48.3% to 60.3% in the ZADF-4 mutant. This result indicates that ZADF-4 may have potential for industrial production of AD.
Chao LIUXian ZHANGZhi-ming RAOMing-long SHAOLe-le ZHANGDan WUZheng-hong XUHui LI
Polyhydroxyalkanoates （PHAs） are a class of natural biopolyesters accumulated intracellularly by many microorganisms. These polymers have attracted particular attention as green plastic in biomedical and industrial applications due to their good biodegradability and bio- compatibility. Poly（3-hydroxybutyrate-co-3-hydroxyvaler- ate） （PHBV） is one of the most common members of PHAs. However, there is no report comparing the properties of PHBV from different groups of producers, e.g., bacteria and haloarchaea. In this study, two types of PHBV copolymers were synthesized in Halogranum amylolyticum and Ralstonia eutropha, respectively, by feeding different carbon sources. They possessed a similar concentration of 3HV monomers （21 tool%） and were named PHBV-H （produced by H. arnylolyticum） and PHBV-B （produced by R. eutropha） based on their source. Interestingly, they exhibited different behaviors especially in thermal stabil- ity, melting temperature, crystallinity percentage, and mechanical properties. Furthermore, the films of PHBV-Hand PHBV-B possessed different surface properties, such as surface roughness, wettability, and surface free energy. The value of hemolysis on the PHBV-H film was lower in comparison with the PHBV-B film, although both values were within the limit of 5 % permissible for biomaterials. Notably, few inactivated platelets adhered to the surface of the PHBV-H film, whereas numerous activated platelets were seen on film PHBV-B. These results indicated that PHBV-H was a better potential component of blood-contact biomaterials than PHBV-B. Our study clearly revealed that the properties of PHAs are source dependent and haloarchaeal species provide a new opportunity for the production of desired PHAs.
Youxi ZhaoZhiming RaoYanfen XuePing GongYizhi JiYanhe Ma
