Polyhydroxyalkanoate biosynthesis and simplified polymer recovery by a novel moderately halophilic bacterium isolated from hypersaline microbial mats

Abstract

Aims: Halophilic micro-organisms have received much interest because of their potential biotechnological applications, among which is the capability of some strains to synthesize polyhydroxyalkanoates (PHA). Halomonas sp. SK5, which was isolated from hypersaline microbial mats, accumulated intracellular granules of poly(3-hydroxybutyrate) [P(3HB)] in modified accumulation medium supplemented with 10% (w/v) salinity and 3% (w/v) glucose. Methods and Results: A cell density of approximately 3Á0 g l À1 was attained in this culture which yielded 48 wt% P(3HB). The bacterial strain was also capable of synthesizing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] when cofed with relevant precursors. Feeding with sodium valerate (0Á7 mol l À1 carbon) at various time intervals within 36 h resulted in 3HV molar fractions ranging from 6 up to 54 mol%. Oil palm trunk sap (OPTS) and seawater as the carbon source and culture medium respectively facilitated a significant accumulation of P(3HB). Simplified downstream processing based on osmotic lysis in the presence of alkali/detergent for both dry and wet biomass resulted in approximately 90-100% recovery of polymers with purity as high as 90%. Weight-average molecular weight (M w ) of the polymers recovered was in the range of 1-2 9 10 6 . Conclusions: Halomonas sp. SK5 was able to synthesize P(3HB) homopolymer as well as P(3HB-co-3HV) copolymer from various carbon sources. Significance and Impact of the Study: This is the first time a comprehensive study of both production and downstream processing is reported for Halomonas spp.

Recent Advances and Challenges towards Sustainable Polyhydroxyalkanoate (PHA) Production

“…This surfactant is a well-known detergent used in the recovery of genetic material. SDS treatment obtained recovery and purity values comparable with other chemical disruption techniques; moreover, this disruption technique obtained similar retrieval with and without biomass pre-treatment [ 169 , 173 ]. The amount of SDS varied between 0.025% and 0.2%, higher concentrations of SDS generated higher purity as result of SDS micelles formation.…”

“…Distilled water achieved high purity (94%) and recovery (98%) percentages; however, the process needed 18 h and lyophilized biomass to reach these high percentages. The process duration improved by adding SDS (0.1%) into the mixture [ 173 ]. In contrast, distilled water disruption treatment with wet biomass obtained recovery (80%) and purity (58%) percentages lower than lyophilized biomass.…”

Hydrolytic Enzymes in Halophilic Bacteria, Properties and Biotechnological Potential

“…Some of halophilic and halotolerant bacteria produce PHAs such as Bacillus megaterium strain H16 (Salgaonkar et al 2013 ), Halomonas sp. SK5 (Rathi et al 2013 ), Halomonas boliviensis LC1 (Quillaguaman et al 2005 ), and Oceanimonas sp. GK1 (Ramezani et al 2014 ).…”

“…PHAs have received much attention because of their biodegradability, biocompatibility, and resembling some properties of petrochemical derived plastics (Rathi et al 2013 ). Some of halophilic and halotolerant bacteria produce PHAs such as Bacillus megaterium strain H16 (Salgaonkar et al 2013 ), Halomonas sp.…”

Production of Polyhydroxyalkanoates by Two Halophilic Archaeal Isolates from Chott El Jerid Using Inexpensive Carbon Sources

“…Halophilic microorganisms are a potential source of PHAs. The production of PHA by bacteria has been extensively studied during the past decades [6]. However, scarce research has been devoted to study the diversity of aerobic PHA-producing archaea at high salinities.…”