Cloning, sequencing, and characterization of lipase genes from a polyhydroxyalkanoate (PHA)-synthesizing Pseudomonas resinovorans

Complete Genome Sequence and Function Gene Identify of Prometryne-Degrading Strain Pseudomonas sp. DY-1

The genus Pseudomonas is widely recognized for its potential for environmental remediation and plant growth promotion. Pseudomonas sp. DY-1 was isolated from the agricultural soil contaminated five years by prometryne, it manifested an outstanding prometryne degradation efficiency and an untapped potential for plant resistance improvement. Thus, it is meaningful to comprehend the genetic background for strain DY-1. The whole genome sequence of this strain revealed a series of environment adaptive and plant beneficial genes which involved in environmental stress response, heavy metal or metalloid resistance, nitrate dissimilatory reduction, riboflavin synthesis, and iron acquisition. Detailed analyses presented the potential of strain DY-1 for degrading various organic compounds via a homogenized pathway or the protocatechuate and catechol branches of the β-ketoadipate pathway. In addition, heterologous expression, and high efficiency liquid chromatography (HPLC) confirmed that prometryne could be oxidized by a Baeyer-Villiger monooxygenase (BVMO) encoded by a gene in the chromosome of strain DY-1. The result of gene knock-out suggested that the sulfate starvation-induced (SSI) genes in this strain might also involve in the process of prometryne degradation. These results would provide the molecular basis for the application of strain DY-1 in various fields and would contribute to the study of prometryne biodegradation mechanism as well.

Conversion of no/low value waste frying oils into biodiesel and polyhydroxyalkanoates

A sustainable bioprocess was developed for the valorization of a no/low value substrate, i.e. waste frying oils (WFOs) with high content of free fatty acids (FFAs), otherwise unsuitable for biodiesel production. The bioprocess was verified using both recombinant (Escherichia coli) and native (Pseudomonas resinovorans) polyhydroxyalkanoates (PHAs) producing cell factories. Microbial fermentation of WFOs provided a 2-fold advantage: i) the reduction of FFAs content resulting into an upgrading of the "exhausted waste oils" and ii) the production of a bio-based microbial polymer. Proper strain designing and process optimization allowed to achieve up to 1.5 g L^-1 of medium chain length, mcl-PHAs, together with an efficient conversion (80% yield) of the treated WFO into biodiesel.

Biodegradation of waste greases and biochemical properties of a novel lipase from Pseudomonas synxantha PS1

A lipase-producing bacterial strain was isolated from oil-well-produced water in Shengli oilfield (Shandong province, China) and was identified as Pseudomonas synxantha by 16S rDNA sequence analysis (named Pseudomonas synxantha PS1). Strain PS1 showed a maximum lipase activity of 10.8 U/mL after culturing for 48 h at 30 °C, with lactose (4 g/L) as carbon source, tryptone (8 g/L) as nitrogen source, olive oil (0.5%, v/v) as inductor, and the initial pH 8.0. Meanwhile, the lipase gene from P. synxantha PS1 was cloned and expressed in Escherichia coli BL21 with the vector pET28a. The novel gene (lipPS1) has an open reading frame of 1425 bp and encodes a 474 aa lipase (LipPS1) sharing the most identity (87%) with the lipase in Pseudomonas fluorescens. LipPS1 preferably acted on substrates with a long chain (C10–C18) of fatty acids. The optimum pH and temperature of the recombinant enzyme were 8.0 and 40 °C, respectively, towards the optimum substrate p-nitrophenyl palmitate. The LipPS1 showed remarkable stability under alkaline conditions and was stable at pH 7.0–10.0 (retaining more than 60% activity). From the organic solvents tests, the lipase was activated by 15% (v/v) methanol (112%), 15% ethanol (127%), and 15% n-butyl alcohol (116%). LipPS1 presented strong biodegradability of waste grease; 93% of waste grease was hydrolyzed into fatty acid after 12 h at 30 °C. This is the first report of the lipase activity and lipase gene obtained from P. synxantha (including wild strain and recombinant strain) and of the recombinant LipPS1 with the detailed enzymatic properties. Also a preliminary study of the biodegradability of waste greases shows the potential value in industry applications.

The two-component GacS-GacA system activates lipA translation by RsmE but not RsmA in Pseudomonas protegens Pf-5

In Pseudomonas spp., the Gac-Rsm signal transduction system is required for the production of lipases. The current model assumes that the system induces lipase gene transcription mediated through the quorum-sensing (QS) system. However, there are no reports of a QS system based upon N-acyl homoserine lactones or the regulation of lipase gene expression in Pseudomonas protegens. In this study, we investigated the regulatory mechanism acting on lipA expression activated by the Gac-Rsm system in P. protegens Pf-5 through deletion and overexpression of gacA, overexpression of rsmA or rsmE, expression of various lacZ fusions, reverse transcription-PCR analysis, and determination of whole-cell lipase activity. The results demonstrated that the GacS-GacA (GacS/A) system activates lipA expression at both the transcriptional and the translational levels but that the translational level is the key regulatory pathway. Further results showed that the activation of lipA translation by the GacS/A system is mediated through RsmE, which inhibits lipA translation by binding to the ACAAGGAUGU sequence overlapping the Shine-Dalgarno (SD) sequence of lipA mRNA to hinder the access of the 30S ribosomal subunit to the SD sequence. Moreover, the GacS/A system promotes lipA transcription through the mediation of RsmA inhibiting lipA transcription via an unknown pathway. Besides the transcriptional repression, RsmA mainly activates lipA translation by negatively regulating rsmE translation. In summary, in P. protegens Pf-5, the Gac-RsmE system mainly and directly activates lipA translation and the Gac-RsmA system indirectly enhances lipA transcription.

Densitometry based microassay for the determination of lipase depolymerizing activity on polyhydroxyalkanoate

A novel method for the assay of polyhydroxyalkanoate (PHA)-degrading ability of triacylglycerol lipases was developed. By applying the natural affinity of lipases towards hydrophobic interfaces, a sensitive and rapid densitometry analysis for the evaluation of hydrolytic activity of lipase droplets towards PHA-coated surface was successfully carried out. We found that 12 out of 14 tested lipases which are of fungal, bacterial and animal origin were able to hydrolyze P(3HB-co-92 mol% 4HB) thin film. The patterns and opacity of the hydrolysis spots of lipases on PHA films allowed easy comparison of PHA-hydrolytic strength of lipases. Lipase from the bacterium Chromobacterium viscosum exhibited the highest PHA-degrading activity. The hydrolytic activity of lipases on water insoluble PHA, emulsified p-nitrophenyl laurate and olive oil were also compared and interestingly some lipases showed better activity when PHA was used as a substrate.