Rhamsan gum is a type of water-soluble exopolysaccharide produced by species of Sphingomonas bacteria. The optimal fermentation medium for rhamsan gum production by Sphingomonas sp. CGMCC 6833 was explored definition. Single-factor experiments indicate that glucose, soybean meal, K(2)HPO(4) and MnSO(4) compose the optimal medium along with and initial pH 7.5. To discover ideal cultural conditions for rhamsan gum production in a shake flask culture, response surface methodology was employed, from which the following optimal ratio was derived: 5.38 g/L soybean meal, 5.71 g/L K(2)HPO(4) and 0.32 g/L MnSO(4). Under ideal fermentation rhamsan gum yield reached 19.58 g/L ± 1.23 g/L, 42.09% higher than that of the initial medium (13.78 g/L ± 1.38 g/L). Optimizing the fermentation medium results in enhanced rhamsan gum production.

The optimal temperature for the microbial polysaccharide fermentation is no higher than 30 °C, which is economically undesirable due to additional cooling cost. To solve this problem in the case of welan gum production, we obtained the high-temperature-tolerant-producing strain, Sphingomonas sp. HT-1 by atmospheric and room-temperature plasma-induced mutation. Using HT-1, we obtained a concentration and 1 % aqueous viscosity of 26.8 ± 0.34 g/L and 3.50 ± 0.05 Pa s at a comparatively higher optimal temperature (37 °C). HT-1 was further characterized to understand the mechanism by which these properties are improved. Results indicated that high yield could be attributed to the following: (1) enhanced intracellular synthesis, demonstrated by an increase in the activities of key enzymes, and (2) accelerated cross-membrane substrate uptake and product secretion, indicated by improved membrane fluidity and permeability. Temperature tolerance could be attributed to the overexpression of the investigated heat shock proteins and oxidative stress proteins.

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In the title coordination polymer, [Ag(C14H8NO2)]n, the AgI cation is coordinated by two O atoms and one N atom from two symmetry-related acridine-9-carboxyl­ate ligands in a distorted trigonal-planar geometry. The metal atoms are connected by the ligands to form chains running parallel to the b axis. π–π stacking inter­actions [centroid-to-centroid distances 3.757 (2)–3.820 (2) Å] and weak Ag⋯O inter­actions further link the chains to form a layer network parallel to the ab plane. The AgI cation is disordered over two positions, with refined site-occupancy factors of 0.73 (3):0.27 (3).

Symmetry codes: (i) Àx; Ày; Àz; (ii) x À 1; y; z; (iii) Àx; Ày þ 1; Àz; (iv) Àx þ 1; Ày þ 1; Àz; (v) x þ 1; y; z; (vi) Àx; Ày; Àz À 1; (vii) x þ 2; y þ 1; z þ 1; (viii) Àx þ 1; Ày þ 1; Àz þ 1.