Chryseobacterium zhengzhouense sp. nov., isolated from groundwater of the well in a vegetable field, and emended description of the genus Chryseobacterium

The characteristics of protein-glutaminase from an isolated Chryseobacterium cucumeris strain and its deamidation application

Protein-glutaminase (PG), a deamidation enzyme commercially derived from Chryseobacterium proteolyticum, is used to improve the solubility and other functional properties of food proteins. In this study, a new PG-producing strain, Chryseobacterium cucumeris ZYF120413-7, was isolated from soil, and it had a high PG yield and a short culture time. It gave the maximum PG activity with 0.557 U/ml on Cbz-Gln-Gly after 12 h of culture, indicating that it was more suitable for PG production. The enzyme activity recovery and purification fold were 32.95% and 161.95-fold, respectively, with a specific activity of 27.37 U/mg. The PG was a pre-pro-protein with a 16 amino acids putative signal peptide, a pro-PG of 118 amino acids, and a mature PG of 185 amino acids. The amino acid sequence identity of PG from strain ZYF120413-7 was 74 and 45%, respectively, to that of PG from C. proteolyticum 9670T and BH-PG. The optimum reaction pH and temperature of PG was 6 and 60°C, respectively. Enzyme activity was inhibited by Cu2+. The optimum PG substrate was Cbz-Gln-Gly, and the Km and Vmax values were 1.68 mM and 1.41 μM mg protein−1 min−1, respectively. Degree of deamidation (DD) of soy protein isolate (SPI) treated by purified PG was 40.75% within the first 2 h and 52.35% after 18 h. These results demonstrated that the PG from C. cucumeris ZYF120413-7 was a promising protein-deamidating enzyme for improving the functionality of food proteins.

Chryseobacterium endophyticum sp. nov., isolated from a maize leaf

A Gram-stain-negative, aerobic, yellow-pigmented, flexirubin-producing, rod-shaped and endophytic bacterium, designated strain CC-YTH209^T, was isolated from a maize leaf and subjected to a taxonomic study. Strain CC-YTH209^T was found to grow at 15-40 °C (optimal 30 °C), at pH 6.0-8.0 (optimal pH 7.0) and in the presence of 0-2 % (optimal 1 %) (w/v) NaCl. On the basis of 16S rRNA gene sequence analysis, strain CC-YTH209^T appeared to belong to the genus Chryseobacterium within the class Flavobacteriia, and was closely related to Chryseobacterium rigui CJ16^T (97.5 % similarity) and Chryseobacterium taeanense PHA3-4^T (96.9 %). The level of DNA-DNA relatedness between strain CC-YTH209^T and Chryseobacterium rigui CJ16^T was 14.4 % (reciprocal, 13.0 %). Phylogenetic analyses based on 16S rRNA genes revealed a distinct taxonomic position attained by strain CC-YTH209^T within the clade that accommodated Chryseobacterium species. The DNA G+C content was 37.2 mol%. Strain CC-YTH209^T contained menaquinone MK-6 as the predominant respiratory quinone and sym-homospermidine as the major polyamine. The major cellular fatty acids of the isolate were iso-C15 : 0, iso-C17 : 0 3-OH and C16 : 1ω6c/C16 : 1ω7c. The polar lipid profile comprised phosphatidylethanolamine and five aminolipids, three lipids, one glycolipid, one aminophospholipid and one phospholipid, which are presently uncharacterized. On the basis of evidence presented in this study, strain CC-YTH209^T is considered to represent a novel species of the genus Chryseobacterium, for which the name Chryseobacterium endophyticum sp. nov. is proposed. The type strain is CC-YTH209^T (=BCRC 80938^T=JCM 31226^T).