Bacterial Resistance against Heavy Metals in Pseudomonas aeruginosa RW9 Involving Hexavalent Chromium Removal

Pseudomonas aeruginosa RW9 is a promising candidate for the bioremediation of chromium hexavalent (Cr(VI)) pollution, as it resists a high concentration of up to 60 mg/L of Cr(VI). Leaving cells exposed to Cr(VI) has large bioreduction potential, implying its capacity to extract the ions from the contaminated medium. In this study, the tolerance for and distribution of Cr(VI) were investigated to identify the cells’ adaptation and removal strategies. Micro-characterization analysis was conducted to assess the effect of Cr(VI) on the cells. The cells’ elongation was observed at higher Cr(VI) concentrations, signifying their adaptation to DNA damage caused by Cr(VI) toxicity. Cr(VI) distribution analysis showed that the strain developed a complex mechanism to adapt to Cr(VI), based on surface-bound (0.46 mg/L), intracellularly accumulated (1.24 mg/L) and extracellular sequestration (6.74 mg/L), which accounted for 85% of the removal efficiency. The extracellular sequestration might be attributable to the production of metabolites, in accordance with the fourier-transform infrared spectroscopy (FTIR) spectra and orcinol analysis that confirmed the presence of a glycolipid biosurfactant, rhamnolipid. Remarkably, the rhamnolipid was slightly induced in the presence of Cr(VI). From the data obtained, it was confirmed that this local strain is well equipped to survive high doses of Cr(VI) and has great potential for application in Cr(VI) bioremediation.

Glycolipid Biosurfactant Production from Waste Cooking Oils by Yeast: Review of Substrates, Producers and Products

Biosurfactants are a microbially synthesized alternative to synthetic surfactants, one of the most important bulk chemicals. Some yeast species are proven to be exceptional biosurfactant producers, while others are emerging producers. A set of factors affects the type, amount, and properties of the biosurfactant produced, as well as the environmental impact and costs of biosurfactant’s production. Exploring waste cooking oil as a substrate for biosurfactants’ production serves as an effective cost-cutting strategy, yet it has some limitations. This review explores the existing knowledge on utilizing waste cooking oil as a feedstock to produce glycolipid biosurfactants by yeast. The review focuses specifically on the differences created by using raw cooking oil or waste cooking oil as the substrate on the ability of various yeast species to synthesize sophorolipids, rhamnolipids, mannosylerythritol lipids, and other glycolipids and the substrate’s impact on the composition, properties, and limitations in the application of biosurfactants.

Screening of a Mannosylerythritol Lipids Producing Strain and Analysis on Its Products

The purpose of this study is to improve the environmental pollution problem, the strains which can produce glycolipid biosurfactant and degrade petroleum hydrocarbons efficiently were screened out in this study. Six strains of glycolipid-producing fungi were isolated from the surface of apple skin by the methods of blood plate and oil plate. After comparing the oil drainage ability of each strain and using PCR to amplify the key genes for the synthesis of glycolipid surfactants, we screened a fungus K6 with emtl sequence. The strain was identified by morphological, physiological and biochemical tests and molecular phylogenetic analysis (5.8S, ITS1, ITS2). Its metabolites were analyzed by TLC and HPLC. The strain was identified as Pseudozyma churashimaensis, which could produce mannose and erythritol. The experiment of petroleum hydrocarbon degradation shows that strain K6 has strong emulsifying ability and the ability of degrading petroleum hydrocarbon. Strain K6, with the strong ability in producing biosurfactants and degrading petroleum, will have broad application prospects for bioremediation of petroleum contaminated environment.