Biosynthesis of rhamnolipid by a Marinobacter species expands the paradigm of biosurfactant synthesis to a new genus of the marine microflora

Abstract

Background In comparison to synthetically derived surfactants, biosurfactants produced from microbial culture are generally regarded by industry as being more sustainable and possess lower toxicity. One major class of biosurfactants are rhamnolipids primarily produced by Pseudomonas aeruginosa. Due to its pathogenicity rhamnolipid synthesis by this species is viewed as being commercially nonviable, as such there is a significant focus to identify alternative producers of rhamnolipids. Results To achieve this, we phenotypically screened marine bacteria for biosurfactant production resulting in the identification of rhamnolipid biosynthesis in a species belonging to the Marinobacter genus. Preliminary screening showed the strain to reduce surface tension of cell-free supernatant to 31.0 mN m−1. A full-factorial design was carried out to assess the effects of pH and sea salt concentration for optimising biosurfactant production. When cultured in optimised media Marinobacter sp. MCTG107b produced 740 ± 28.3 mg L−1 of biosurfactant after 96 h of growth. Characterisation of this biosurfactant using both HPLC–MS and tandem MS showed it to be a mixture of different rhamnolipids, with di-rhamnolipid, Rha-Rha-C10-C10 being the most predominant congener. The strain exhibited no pathogenicity when tested using the Galleria mellonella infection model. Conclusions This study expands the paradigm of rhamnolipid biosynthesis to a new genus of bacterium from the marine environment. Rhamnolipids produced from Marinobacter have prospects for industrial application due to their potential to be synthesised from cheap, renewable feed stocks and significantly reduced pathogenicity compared to P. aeruginosa strains.

Toxicity Profiling of Biosurfactants Produced by Novel Marine Bacterial Strains

“…Following the initial screening process, two novel bacterial strains, MCTG107b and MCTG214(3b1), were identified to produce rhamnolipids with properties of enhanced surface tension reduction for potential commercial exploitation. The screening, cultivation process, identification, and isolation of these biosurfactants has been described in detail in previous reports by Twigg et al (2018) [ 11 ] and Tripathi et al (2019) [ 12 ]. Strains MCTG107b and MCTG214(3b1) belong to the genus Marinobacter and Pseudomonas , respectively.…”

“…MCTG214(3b1) and Marinobacter sp. MCTG107b appeared to be non-pathogenic as illustrated via the Galleria mellonella infection model [ 11 , 12 ].…”

Microbial biosurfactant research: time to improve the rigour in the reporting of synthesis, functional characterization and process development

“…Typically, hydrophobic (such as fatty acids, plant oils) and/or hydrophilic (such as carbohydrates, polyols) substrates are used, for which highly pure standards are available. The monitoring of substrate concentration in the culture medium throughout the fermentation is often a key step in the optimization of microbial biosurfactant production (Van Bogaert et al ., 2007; Funston et al ., 2017; Tripathi et al ., 2019).…”

“…Where this is the case the exploitation of these surface‐active compounds for commercial application becomes complicated due to regulations relating to the cultivation of pathogenic species and also the potential for products obtained from these cultures to be contaminated with harmful virulence factors (Campos et al ., 2013). Therefore, a large amount of current research is focused on either the identification of microbes producing surface‐active compounds that have non‐pathogenic taxonomic affiliations or engineering surface‐active compound biosynthesis pathways in to non‐pathogenic host strains (Müller and Hausmann, 2011; Müller et al ., 2011; Funston et al ., 2016; Twigg et al ., 2018; Tripathi et al ., 2019).…”

Planococcus Species – An Imminent Resource to Explore Biosurfactant and Bioactive Metabolites for Industrial Applications

“…Serratia, Arthrobacter, Staphylococcus, Brevibacterium, Acinetobacter , and Streptomyces were reported around 2–3% for novel BS production ( Mapelli et al, 2017 ). Some of the recently reported stains include Marinobacter ( Tripathi et al, 2019 ), Cyberlindnera ( Balan et al, 2019 ), Acromobacter ( Deng et al, 2016 ), Buttiauxella ( Marzban et al, 2016 ), and Paracoccus ( Antoniou et al, 2015 ). Nevertheless, BS production by marine microbes remains largely unexplored due to the difficulties to cultivate them in the laboratories ( Gudiña et al, 2016 ; Tripathi et al, 2018 ; McCarthy et al, 2019 ).…”