Enhanced rhamnolipid production in Burkholderia thailandensis transposon knockout strains deficient in polyhydroxyalkanoate (PHA) synthesis

Abstract

Microbially produced rhamnolipids have significant commercial potential; however, the main bacterial producer, Pseudomonas aeruginosa, is an opportunistic human pathogen, which limits biotechnological exploitation. The non-pathogenic species Burkholderia thailandensis produces rhamnolipids; however, yield is relatively low. The aim of this study was to determine whether rhamnolipid production could be increased in Burkholderia thailandensis through mutation of genes responsible for the synthesis of the storage material polyhydroxyalkanoate (PHA), thereby increasing cellular resources for the production of rhamnolipids. Potential PHA target genes were identified in B. thailandensis through comparison with known function genes in Pseudomonas aeruginosa. Multiple knockout strains for the phbA, phbB and phbC genes were obtained and their growth characteristics and rhamnolipid and PHA production determined. The wild-type strain and an rhamnolipid (RL)-deficient strain were used as controls. Three knockout strains (ΔphbA1, ΔphbB1 and ΔphbC1) with the best enhancement of rhamnolipid production were selected for detailed study. ΔphbB1 produced the highest level of purified RL (3.78 g l−1) compared to the wild-type strain (1.28 g l−1). In ΔphbB1, the proportion of mono-rhamnolipid was also increased compared to the wild-type strain. The production of PHA was reduced by at least 80% in all three phb mutant strains, although never completely eliminated. These results suggest that, in contrast to Pseudomonas aeruginosa, knockout of the PHA synthesis pathway in Burkholderia thailandensis could be used to increase rhamnolipid production. The evidence of residual PHA production in the phb mutant strains suggests B. thailandensis possesses a secondary unelucidated PHA synthesis pathway.Electronic supplementary materialThe online version of this article (10.1007/s00253-017-8540-x) contains supplementary material, which is available to authorized users.

Fatty acid synthesis pathway provides lipid precursors for rhamnolipid biosynthesis in Burkholderia thailandensis E264

“…This creates an opportunity to genetically modify B. thailandensis for increased rhamnolipid production, by creating mutants unable to divert FAS II products to other metabolic cell processes. A clear example is the enhanced rhamnolipid production in polyhydroxyalkanoate (PHA)-deficient mutants of B. thailandensis (Funston et al 2017). Contrarily, PHA-deficient mutants of P. aeruginosa did not produce significantly higher rhamnolipid yields compared to wild type; however, rhamnolipid-deficient mutants produced significantly higher yields of PHA (Choi et al 2011).…”

Identification and characterisation of short chain rhamnolipid production in a previously uninvestigated, non-pathogenic marine pseudomonad

“…Recently, RL production in B. thailandensis has been linked to polyhydroxyalkanoate (PHA) synthesis and storage. B. thailandensis PHA synthase mutants produce significantly higher yields of RL in comparison to the wild-type strain (Funston et al 2017 ). It should, however, be noted that the longer chain RL congeners synthesised by B. thailandensis possess differing activities to the shorter chain congeners synthesised by P. aeruginosa , which could have a marked effect on their potential biotechnological application (Elshikh et al 2017 ).…”

Marine derived biosurfactants: a vast potential future resource

“…Another approach to increase the BS yield is to silence the genes competing with the BS production pathway. For example, Funston et al ( 2017 ) knocked-out the polyhydroxyalkanoate (PHA) pathway synthesis genes for enhanced rhamnolipid production. The halophile Halomonas species are ubiquitous in marine environments and produces BE which effectively emulsifies hydrocarbons and other petroleum contaminants.…”