Bacterial synthesis of poly(hydroxybutyrate- co-hydroxyvalerate) using carbohydrate-rich mahua (Madhuca sp.) flowers

Abstract

Aims: The objective of the present work was to utilize an unrefined natural substrate namely mahua (Madhuca sp.) flowers, as a carbon source for the production of bacterial polyhydroxyalkanoate (PHA) copolymer by Bacillus sp‐256. Methods and Results: In the present work, three bacterial strains were tested for PHA production on mahua flower extract (to impart 20 g l−1 sugar) amongst which, Bacillus sp‐256 produced higher concentration of PHA in its biomass (51%) compared with Rhizobium meliloti (31%) or Sphingomonas sp (22%). Biosynthesis of poly(hydroxybutyrate‐co‐hydroxyvalerate) – P(HB‐co‐HV) – of 90 : 10 mol% by Bacillus sp‐256 was observed by gas chromatographic analysis of the polymer. Major component of the flower is sugars (57% on dry weight basis) and additionally it also contains proteins, vitamins, organic acids and essential oils. The bacterium utilized malic acid present in the substrate as a co‐carbon source for the copolymer production. The flowers could be used in the form of aqueous extract or as whole flowers. PHA content of biomass (%) and yield (g l−1) in a 3·0‐l stirred tank fermentor after 30 h of fermentation under constant pH (7) and dissolved oxygen content (40%) were 54% and 2·7 g l−1, respectively. Corresponding yields for control fermentation with sucrose as carbon source were 52% and 2·5 g l−1. The polymer was characterized by proton NMR. Conclusions: Utilization of mahua flowers, a natural substrate for bacterial fermentation aimed at PHA production, had additional advantage, as the sugars and organic acids present in the flowers were metabolized by Bacillus sp‐256 to synthesize P(HB‐co‐HV) copolymer. Significance and Impact of the Study: Literature reports on utilization of suitable cheaper natural substrate for PHA copolymer production is scanty. Mahua flowers used in the present experiment is a cheaper carbon substrate compared with several commercial substrates and it is rich in main carbon as well as co‐carbon sources that can be utilized by bacteria for PHA copolymer production.

A novel Bacillus sp. accumulating poly (3-hydroxybutyrate-co-3-hydroxyvalerate) from a single carbon substrate

“…This is a signiWcant result because there have been only a few reports of P (3HB-co-3HV) synthesis from a single carbon source [22]. Composition of the carbon substrate used for fermentation and utilization of appropriate bacterial strain control the production of copolymers of PHB [23]. When tested in combination with propionic acid, the precursor for 3HV copolymer accumulation, at a concentration of 2 ml/l, Bacillus sp.…”

Production of polyhydroxyalkanoate from starch by the native isolate Bacillus cereus CFR06

“…However, PHB does not possess material properties because of its crystalline and brittle nature. The co-polymer containing both PHB and PHV (poly-b-hydroxyvalerate) is more flexible and tougher and of greater industrial interest and can be obtained by the co-feeding propionate and pentonoate (Anil-Kumar et al 2007;Full et al 2006).…”

“…Reports suggesting the use of Bacillus for the production of a range of different PHAs by utilizing different carbon sources are known. These include incorporation of the tercopolymer of 3HB, HV, and 3HHX (3-hydroxy-hexanoate) utilizing b-caprolactone (Labuzek and Radecka 2001), P(3HB-co-3HV) from different carbon sources (Tajima et al 2003), PHB co-PHV in mahua flowers (Anil-Kumar et al 2007), from sucrose (Shamala et al 2003), and PHBs from soy molasses oligosaccharides (Full et al 2006), sugarcane molasses, and corn steep liquor (Gouda et al 2001). The co-polymer synthesis from structurally unrelated carbon sources suggests that Bacillus has the potential for production of a new PHA co-polymer using different substrates (Valappil et al 2007b).…”

Improved Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Produced byComamonassp. EB172 Utilizing Volatile Fatty Acids by Regulating the Nitrogen Source

“…One of the limiting factors for the economic production of PHAs is the cost of feedstock, which contributes up to 40% of the total operating costs [2]. Several successful studies have been reported on PHA production from cheap and renewable carbon sources, for example, date syrup, mahua flowers, and palm oil mill effluent (POME) [3–5]. Ntaikou et al [6] reported that combined biohydrogen and biopolymers were produced from olive oil mill wastewater by two-stage reactor system with poly-3-hydroxybutyrate, P(3HB) yield of 8.94% per dry biomass weight.…”