Polyhydroxyalkanoate biosynthesis by Hydrogenophaga pseudoflava DSM1034 from structurally unrelated carbon sources

Abstract

In the present paper we report the exclusive microbial preparation of polyhydroxyalkanoates (PHA) containing 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV) and 4-hydroxybutyrate (4HB) as comonomers through the use of unexpensive carbon sources such as whey from dairy industry. Polymers were produced by growing H. pseudoflava DSM 1034 in minimal medium supplemented with sucrose, lactose or whey without any co-substrate added. The chemical and physical properties of the polymers were fully characterized by GPC, DSC, TGA analyses and the composition by GC and (1)H NMR examinations to especially confirm the content of different monomeric units. The presence of 4HB units into PHA samples is particularly aimed in thermoplastic applications where greater flexibility is required and conventional rigid PHAs tend to fail. Usually the insertion of 4HB into chain backbone consisting of 3-hydroxyalkanoates requires expensive carbon sources mostly of petrochemical origin. According to our study the production of P(3HB-co-3HV-co-4HB) terpolymer can be obtained directly by the use of lactose or waste raw materials such as cheese whey as carbon sources. Although the amount of 4HB in the produced terpolymers was usually low and not exceeding 10% of the total molar composition, a PHA containing 18.4% of 4HB units was produced in 1 step fermentation process from this structurally unrelated carbon sources. The crystallinity of the terpolymer is basically to be markedly affected with respect to that of conventional PHAs, thus obtaining a comparatively less rigid material and easier to be processed.

Comparing Chemical and Enzymatic Hydrolysis of Whey Lactose to Generate Feedstocks for Haloarchaeal Poly(3-hydroxybutyrate-co-3- hydroxyvalerate) Biosynthesis

“…Under similar conditions (no supply of structurally related 3HV-precursors), most other microbial production strains accumulated the homopolyester PHB from lactose-derived substrates. As a remarkable exception, Povolo and colleagues [25] reported the production of PHBHV copolyesters with small amounts of 3HV by H. pseudoflava on lactose as carbon source. Replacing pure lactose by whey, even the incorporation of 4-hydroxybutyrate (4HB) building block was detected by these authors.…”

“…These findings were in contrast to previous results from the same group [24] and our own works [17], where recovered PHA samples from whey-and lactose based cultivation of H. pseudoflava contained 3HB as the only monomeric building block. Based on these findings, Povolo et al [25] assumed that one or more unknown components, present in both yeast extract and in whey, might cause 4HB production and its following incorporation into the biopolyester. It will be highly intriguing to trace and identify these 4HB-precursor compound, together with the strain´s unknown biochemical pathways responsible for production and assembly of copolyesters containing 3HV building blocks.…”

“…Hence, new (bio) products from whey are aspired, especially such as those produced by the action of either Gram-positive or Gram-negative microbial production strains [16,23]. Investigation of whey-based PHA biosynthesis started almost 20 years ago and encompassed the implementation of both Gram-negative wild type strains like Haloferax mediterranei [17], Sinorhizobium meliloti [24], Hydrogenophaga pseudoflava [17,24,25], Pseudomonas hydrogenovora [18], or Methylobacterium sp. [26], and genetically engineered Gram-negative organisms, predominately Escherichia coli [27,28] and Cupriavidus necator [29].…”

Morphology and thermal properties of biodegradable poly(hydroxybutyrate-co-hydroxyvalerate)/tungsten disulphide inorganic nanotube nanocomposites

“…The production of PHA biopolymers originates in genetically controlled, energy storage procedures of a number of microorganisms under certain environmental situations [2,3]. Poly(hydroxybutyrate co hydroxyvalerate) (PHBV), the most common PHA copolyester, can be transformed using conventional thermoplastics processing equipment, and has properties compa rable to a range of petroleum based plastics, making it appealing as a biodegradable engineering material.…”

Burkholderia sp. cadmium tolerance mechanism and its influence in phytoremediation

“…This Gram-negative bacteriumis a hydrogen-oxidizing bacteria, isolated from water, mud and soil, and previously classified as Pseudomonas genus . It has been studied mainly due its ability to accumulate polyhydroxyalkanoates (PHA) from different substrates (POVOLO et al, 2012), besides that enzymes responsible for the oxidation of CO to carbon dioxide (carbon monoxide dehydrogenases (CO-DH) were described in H. pseudoflava KIM, 1999), which confirms that this bacterium needs RubisCO enzyme to use CO 2 as carbon source.…”