Production of poly-3-hydroxybutyrate by Bacillus sp. JMa5 cultivated in molasses media

Statistical optimization of medium components for enhanced acetoin production from molasses and soybean meal hydrolysate

The nutritional requirements for acetoin production by Bacillus subtilis CICC 10025 were optimized statistically in shake flask experiments using indigenous agroindustrial by-products. The medium components considered for initial screening in a Plackett-Burman design comprised a-molasses (molasses submitted to acidification pretreatment), soybean meal hydrolysate (SMH), KH(2)PO(4).3H(2)O, sodium acetate, MgSO(4).7H(2)O, FeCl(2), and MnCl(2), in which the first two were identified as significantly (at the 99% significant level) influencing acetoin production. Response surface methodology was applied to determine the mutual interactions between these two components and optimal levels for acetoin production. In flask fermentations, 37.9 g l(-1) acetoin was repeatedly achieved using the optimized concentrations of a-molasses and SMH [22.0% (v/v) and 27.8% (v/v), respectively]. a-Molasses and SMH were demonstrated to be more productive than pure sucrose and yeast extract plus peptone, respectively, in acetoin fermentation. In a 5-l fermenter, 35.4 g l(-1) of acetoin could be obtained after 56.4 h of cultivation. To our knowledge, these results, i.e., acetoin yields in flask or fermenter fermentations, were new records on acetoin fermentation by B. subtilis.

Polyhydroxyalkanoate (PHA) biosynthesis from structurally unrelated carbon sources by a newly characterized Bacillus spp

A newly acquired polyhydroxyalkanoate (PHA) producing Bacillus spp. was identified to be a strain of Bacillus cereus using a range of microbiological and molecular techniques. This strain, named B. cereus SPV, was found to be capable of using a wide range of carbon sources including glucose, fructose, sucrose, various fatty acids and gluconate for the production of PHAs, an advantage for the commercial production of the polymers. The media used for the polymer production was novel in the context of the genus Bacillus. The PHA, once produced, was found to remain at a constant maximal concentration, without any degradation, a great advantage for the commercial production of the PHAs. This particular strain of Bacillus spp. was able to synthesize various PHAs with 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV) and 4-hydroxybutyrate (4HB)-like monomer units from structurally unrelated carbon sources such as fructose, sucrose and gluconate. This is the first report of the incorporation of a 4HB related monomer containing PHA by the genus Bacillus and from structurally unrelated carbon sources. The PHAs isolated had molecular weights ranging between (0.4 and 0.8) x 10(6) and low polydispersity index values (M(W)/M(N)) ranging from 2.6 to 3.4.

Polyhydroxyalkanoates in Gram-positive bacteria: insights from the genera Bacillus and Streptomyces

Gram-positive bacteria, notably Bacillus and Streptomyces, have been used extensively in industry. However, these microorganisms have not yet been exploited for the production of the biodegradable polymers, polyhydroxyalkanoates (PHAs). Although PHAs have many potential applications, the cost of production means that medical applications are currently the main area of use. Gram-negative bacteria, currently the only commercial source of PHAs, have lipopolysaccharides (LPS) which co-purify with the PHAs and cause immunogenic reactions. On the other hand, Gram- positive bacteria lack LPS, a positive feature which justifies intensive investigation into their production of PHAs. This review summarizes currently available knowledge on PHA production by Gram- positive bacteria especially Bacillus and Streptomyces. We hope that this will form the basis of further research into developing either or both as a source of PHAs for medical applications.

Production system for biodegradable polyester polyhydroxybutyrate by Corynebacterium glutamicum

A biosynthetic pathway for poly(3-hydroxybutyrate) [P(3HB)] production by Corynebacterium glutamicum was developed by introducing the phbCAB operon derived from Ralstonia eutropha. P(3HB) synthase activity was detected in this recombinant C. glutamicum carrying a cell surface protein gene promoter. Intracellular P(3HB) was microscopically observed as inclusion granules and its content was calculated to be 22.5% (w/w) with a number average molecular weight of 2.1x10(5) and a polydispersity of 1.63.

Conversion of agricultural feedstock and coproducts into poly(hydroxyalkanoates)

Aside from their importance to the survival and general welfare of mankind, agriculture and its related industries produce large quantities of feedstocks and coproducts that can be used as inexpensive substrates for fermentative processes. Successful adoption of these materials into commercial processes could further the realization of a biorefinery industry based on agriculturally derived feedstocks. One potential concept is the production of poly(hydroxyalkanoate) (PHA) polymers, a family of microbial biopolyesters with a myriad of possible monomeric compositions and performance properties. The economics for the fermentative production of PHA could benefit from the use of low-cost agricultural feedstocks and coproducts. This mini-review provides a brief survey of research performed in this area, with specific emphasis on studies describing the utilization of intact triacylglycerols (vegetable oils and animal fats), dairy whey, molasses, and meat-and-bone meal as substrates in the microbial synthesis of PHA polymers.

Biosynthesis of medium-chain-length poly(hydroxyalkanoates) from soy molasses

Pseudomonas corrugata was selected from a screening process for the bioconversion of inexpensive soy molasses into medium-chain-length poly(hydroxyalkanoates) (mcl-PHA). We obtained yields of 1.5 g cell dry weight (CDW)/l culture with growth medium supplemented with 2% (w/v) soy molasses, and of an average of 3.4 g CDW/l with 5% (w/v) soy molasses. Crude PHAs were obtained at 5-17% of CDW. The most prominent repeat-unit monomers in the PHAs were 3-hydroxydodecanoate, 3-hydroxyoctanoate, 3-hydroxydodecanoate, and 3-hydroxytetradecenoate. This work represents the first description of fermentative mcl-PHA production from the soy molasses.