Production of lipase and extracellular polymeric substances by the lipid-degrading bacterium Burkholderia arboris strain JYK2 in response to different substrates

Abstract

Characterization of lipid-degrading microorganisms and understanding their metabolite production mechanisms are essential for enhancing biodegradation efficiency of lipid-rich wastewater. In this study, we isolated Burkholderia arboris strain JYK2, which demonstrated lipid degradation at 46.29 mg/(l • h) with lipase activity reaching 59.92 U/ml when lipid was provided as the sole carbon source. Experimental results revealed that strain JYK2 secretes lipase in media containing lipids and fatty acids but not in glycerol-containing media, a phenomenon likely attributable to quorum sensing mechanisms. Furthermore, extracellular polymeric substances (EPS) were produced in the presence of lipids and fatty acids. Compositional analysis showed that EPS primarily consisted of proteins (approximately 50%) and polysaccharides (approximately 25%). This protein-rich characteristic conferred high hydrophobicity to the EPS, contributing to its lipase adsorption capacity as verified in this study. Additionally, biosurfactant activity was detected in the EPS produced by JYK2. These functions collectively enhance substrate utilization by microorganisms and promote lipid biodegradation. However, minimal EPS production was observed at low fatty acid concentrations, suggesting that the EPS production mechanism cannot be solely attributed to quorum sensing. This study provides insights into the interactions between lipid-degrading bacteria, lipase production, and EPS functionality, which are crucial for optimizing biological treatment of lipid-rich wastewater.

Keywords: Burkholderia; Extracellular polymeric substance; Lipase; Lipid biodegradation.

Fig. 1

Lipase activity of isolated strains (Day6): Strains JYK1 ~ 3 were isolated from Kesennuma, JYF1 ~ 3 were isolated from Fukushima and JYM1 ~ 3 were isolated from Tome. Ctrl referred to a negative control group without bacteria inoculation in the medium

Fig. 2

Lipase activity in different substrates (a) or different initial concentrations of lipid and fatty acid (b). FA- fatty acid, Gly-glycerol and Ctrl-Milli-Q water

Fig. 3

Substrate loss and bacterial growth in different substrates: lipid (a) & (b); fatty acids (c) & (d); glycerol (e) & (f)

Fig. 4

EPS production by JYK2 at different substrates in lipids (a) and fatty acids (b)

Fig. 5

Composition of EPS produced by JYK2. (a) and (b) refer to the concentrations and proportions of polysaccharides (PS) and proteins (PN) in EPS separately at the initial lipids concentration of 20 ml/l

Fig. 6

Proposed mechanism of lipase production by B. arboris strain JYK2. (a) In lipids and fatty acids containing media: (1) Bacteria aggregate around lipid droplets; (2) Local bacteria density increase on oil-water interface; (3) Quorum sensing signal molecules were combined with relevant receptors and later trigger the expression of lipase & EPS production gene such as lipA; (4) Lipases are produced. (b) In glycerol containing media: (1) Bacteria are evenly distributed in media; (2) Bacteria density is low, and thus, quorum sensing signal molecules do not exceed the threshold concentration; (3) Lipases are not produced