Biodegradation of penicillin G sodium by Sphingobacterium sp. SQW1: Performance, degradation mechanism, and key enzymes.

Biodegradation is an efficient and cost-effective approach to remove residual penicillin G sodium (PGNa) from the environment. In this study, the effective PGNa-degrading strain SQW1 (Sphingobacterium sp.) was screened from contaminated soil using enrichment technique. The effects of critical operational parameters on PGNa degradation by strain SQW1 were systematically investigated, and these parameters were optimized by response surface methodology to maximize PGNa degradation. Comparative experiments found the extracellular enzyme to completely degrade PGNa within 60 min. Combined with whole genome sequencing of strain SQW1 and LC-MS analysis of degradation products, penicillin acylase and ß-lactamase were identified as critical enzymes for PGNa biodegradation. Moreover, three degradation pathways were postulated, including ß-lactam hydrolysis, penicillin acylase hydrolysis, decarboxylation, desulfurization, demethylation, oxidative dehydrogenation, hydroxyl reduction, and demethylation reactions. The toxicity of PGNa biodegradation intermediates was assessed using paper diffusion method, ECOSAR, and TEST software, which showed that the biodegradation products had low toxicity. This study is the first to describe PGNa-degrading bacteria and detailed degradation mechanisms, which will provide new insights into the PGNa biodegradation.

Physiological metabolic topology analysis of Halomonas elongata DSM 2581T in response to sodium chloride stress.

The halophilic bacterium Halomonas elongata DSM 2581T generally adapts well to high level of salinity by biosynthesizing ectoine, which functions as an important compatible solute protecting the cell against external salinity environment. Halophilic bacteria have specific metabolic activities under high-salt conditions and are gradually applied in various industries. The present study focuses on investigating the physiological and metabolic mechanism of H. elongata DSM 2581T driven by the external salinity environment. The physiological metabolic dynamics under salt stress were investigated to evaluate the effect of NaCl stress on the metabolism of H. elongata. The obtained results demonstrated that ectoine biosynthesis transited from a nongrowth-related process to a growth-related process when the NaCl concentration varied from 1% to 13% (w/v). The maximum biomass (Xm = 41.37 g/L), and highest ectoine production (Pm = 12.91 g/L) were achieved under 8% NaCl. Moreover, the maximum biomass (Xm ) and the maximum specific growth rates (µm ) showed a first rising and then declining trend with the increased NaCl stress. Furthermore, the transcriptome analysis of H. elongata under different NaCl concentrations demonstrated that both 8% and 13% NaCl conditions resulted in increased expressions of genes involved in the pentose phosphate pathway, Entner-Doudoroff pathway, flagellar assembly pathway, and ectoine metabolism, but negatively affected the tricarboxylic acid cycle and fatty acid metabolism. At last, the proposed possible adaptation mechanism under the optimum NaCl concentration in H. elongata was described.