<Emphasis Type="Italic">Actinoplanes deserti</Emphasis> sp. nov., isolated from a desert soil sample

A novel actinomycete, designated strain YIM CF22^T, was isolated from a desert soil sample collected from Turpan in Xinjiang Uyghur Autonomous Region, north-western China. The taxonomic position of the strain YIM CF22^T is described based on a polyphasic approach. Strain YIM CF22^T was found to form irregular sporangia on agar media. It contains meso-diaminopimelic acid in the cell wall peptidoglycan. The major menaquinone was identified as MK-9(H₄); the polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, two unidentified phospholipids and two unidentified glycolipids. The whole cell sugars were found to be ribose, mannose, galactose, glucose and xylose. The major cellular fatty acids were found to be (>?5%) iso-C_16:0 (43.5%), anteiso-C_17:0 (10.2%), iso-C_15:0 (7.1%), C_17:1 ω8c (6.3%) and iso H-C_16:1 (5.9%). The G+C content was determined to be 70.8%. 16S rRNA gene sequence analysis of strain YIM CF22^T showed high similarity (97.0%) to Actinoplanes rishiriensis NBRC 108556^T. The strain also showed high 16S rRNA gene sequence similarities to Verrucosispora sediminis CGMCC 4.3550^T (96.9%) and Micromonospora tulbaghiae DSM 45142^T (96.8%). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain YIM CF22^T clusters with A. rishiriensis NBRC 108556^T, Actinoplanes globisporus JCM 3186^T and Actinoplanes rhizophilus NEAU-A-2^T. Based on the differential phenotypic characteristics and the results of DNA–DNA relatedness and phylogenetic analysis, it is proposed that strain YIM CF22^T represents a novel species of the genus Actinoplanes, for which the name Actinoplanes deserti sp. nov. is proposed. The type strain is YIM CF22^T (=?KCTC 39543^T?=?CCTCC AB2018113^T).     

Biological pretreatment of rice straw with Streptomyces griseorubens JSD-1 and its optimized production of cellulase and xylanase for improved enzymatic saccharification efficiency

Biological pretreatment of rice straw and production of reducing sugars by hydrolysis of bio-pretreated material with Streptomyces griseorubens JSD-1 was investigated. After 10 days of incubation, various chemical compositions of inoculated rice straw were degraded and used for further enzymatic hydrolysis studies. The production of cellulolytic enzyme by S. griseorubens JSD-1 favored the conversion of cellulose to reducing sugars. The culture medium for cellulolytic enzyme production by using agro-industrial wastes was optimized through response surface methodology. According to the response surface analysis, the concentrations of 11.13, 20.34, 4.61, and 2.85 g L^?1 for rice straw, wheat bran, peptone, and CaCO₃, respectively, were found to be optimum for cellulase and xylanase production. Then the hydrolyzed spent Streptomyces cells were used as a nitrogen source and the maximum filter paper cellulase, carboxymethylcellulase, and xylanase activities of 25.79, 78.91, and 269.53 U mL^?1 were achieved. The crude cellulase produced by S. griseorubens JSD-1 was subsequently used for the hydrolysis of bio-pretreated rice straw, and the optimum saccharification efficiency of 88.13% was obtained, indicating that the crude enzyme might be used instead of commercial cellulase during a saccharification process. These results give a basis for further study of bioethanol production from agricultural cellulosic waste.     

Effect of a disulfide bond on mevalonate kinase

Mevalonate kinase is one of ATP-dependent enzymes in the mevalonate pathway and catalyzes the phosphorylation of mevalonate to form mevalonate 5-phosphate. In animal cells, it plays a key role in regulating biosynthesis of cholesterol, while in microorganisms and plants, it is involved in the biosynthesis of isoprenoid derivatives that are one of the largest groups of natural products. Crystal structure and sequence alignment show that a unique disulfide bond exists in mevalonate kinase of thermostable species Methanococcus jannaschii, but not in rat mevalonate kinase. In the present study, we investigated the effect of the disulfide bond in M. jannaschii mevalonate kinase and an engineered disulfide bond in rat mevalonate kinase mutant A141C on the properties of enzymes through characterization of their wild-type and variant enzymes. Our result suggests that the Cys107-Cys281 disulfide bond is important for maintaining the conformation and the thermal activity of M. jannaschii mevalonate kinase. Other interactions could also have contributions. The thiol-titration and fluorescence experiment further indicate that rat mevalonate kinase A141C variant enzyme has a new disulfide bond, which makes the variant protein enhance its thermal activity and resist to urea denaturation.