PHB Production

Previously, Yu et al (2005) studied the increase of a co-biopolymer of PHBV by Ralstonia eutropha in a continuous stirred tank reactor. It was found that the productivity rate increased when sodium propionate was used as the carbon source. Later, Yezza et al (2007) investigated the use of maple sap as a carbon for PHB production by A. latus. The productivity of PHB reached 2.6 gH h-i. 

H.,2010. Kinetic model for polyhydroxybutyrate (PHB) production by Hydrogenophaga pseudoflcwa and verification of growth conditions. Afr. J. Biot. 9, 3151-3157. 

For the production of PHB, a specially selected bacteria is used. They grow in aqueous media during air injection at 35°C. At the end of the fermentation process about 80% of cell dry weight consists of PHB. Production is about 100 kg PHB/m of medium (Fig. 7). 

Poly-p-hydroxybutyrate (PHB) is a biodegradable thermoplastic that is produced by several microorganism. The PHB synthesis has been characterized in Alcaligens eutrophus and the operon involved in PHB production has been cloned. Recombinant E. coli strains that can produce high levels of PHB have been constmcted (39). 

The ready availability of starch-based industrial wastes and their renewable nature merit their use as substrates for poly-betahydroxybutyrate (PHB) production from activated sludge. This would not only utilize the excess sludge generated and reduce the load on landfills, but would also contribute to reduction in the cost of PHB production by avoiding sterile conditions and pure carbon sources for maintenance and growth of pure cultures. PHB content is the most important factor affecting the production cost of PHB due to its effect on PHB yield and recovery efficiency, followed by cultural conditions and carbon substrates used (Khardenavis, 2007). 

Integration of PHB Production Process into the Sugarcane Mill... 

After biosynthesis of the polyester and separation of the bacterial biomass from the supernatant, the required recovery process (typically a solid-liquid extractiOTi procedure) can constitute another not negligible cost factor, especially in large-scale production. Here extraction solvents that can easily be recycled will be of interest [53]. In order not to leave the patterns of sustainability in biopolymer production, it will be indispensable to concentrate the development of new extraction processes on such recyclable solvents that are also of environmentally sound nature [54], Typical harmful chlorinated solvents like chloroform must be avoided. A PHB production process embedded in an ethanol production plant has the advantage to utilise the medium chain length alcohol fraction (fusel alcohols) from the distillery step, consisting mainly of iso-pentanol. The application of the fusel alcohols as extracting solvents unites two important points On the one hand, this liquid normally constitutes a surplus product that has little market value. When used as an extraction solvent the costs for alternative solvents are saved. Furthermore, this extraction solvent is less harmful to handle than the classical extraction solvent chloroform [27],... 

Fig. 2 Closed carbon cycle in PHB production integrated in a sugar mill with ethanol...

Until today, biotechnological production of PHB requires more energy than the production of petrochemical plastics [64]. The integration of PHB production into the sugarcane mill unites several advantages ... 

The readiness of the industry to use PHB in the range of low price materials has failed dimng the last years because of the costs of PHB. Production of PHB or the PHB/PHV-copolymer under the trade name Biopol for technical use was abandoned, while in the last years efforts to use PHB for the medical sphere and niche products have continued. 

Archer Daniels Midland Co.) PLA and PHB production capability being developed. 

Jarute G, Kainz A, SchroU G, Baena JR, Lendl B (2004) On-line determination of the intracellular poly(P-hydroxybutyric acid) content in transformed Escherichia coli and glucose during PHB production using stopped-flow attenuated total reflection FT-IR spectrometry. Anal Chem 76 6353-6358... 

Khanna S, Srivastava AK (2005b) Statistical media optimization studies for growth and PHB production by Ralstonia eutropha. Process Biochem 40 2173-2182 Khanna S, Srivastava AK (2007) Production of poly(3-hydroxybutyric-co-3-hydroxyvaleric aicd) having a high hydroxyvalerate content with valeric acid feeding. J Ind Microbiol Biotechnol 34 457-461... 

Park WH, Jeong L, Yoo DI, Hudson S (2004) Effect of chitosan on morphology and conformation of electrospun silk fibroin nanofibers. Polymers 45 7151-7157 Patnaik PR (2006) Dispersion optimization to enhance PHB production in fed-batch cultures of Ralstonia eutropha. Bioresour Technol 97 1994-2001 Patra SN, Bhattacharyya D, Ray S, Easteal AJ (2009) Electrospun poly(lactic add) based conducting nanofibrous networks. lOP Conference Series Mater Sci Eng doi 10.1088/1757-899X/4/l/012020 Peh KSH, Sodhi NS, de Jong J, Sekercioglu CH, Yap CAM, Lim SLH (2006) Conservation value of degraded habitats for forest birds in southern Peninsular Malaysia. Divers Distrib 12 572-581... 

As shown in previous studies oxygen concentration can modulate PHB production in rhizobia. It was demonstrated that oxygen limitation can enhance PHB synthesis in Rhizobium spp cells. The incubation of exponential phase cells of S. meliloti 41 under low oxygen generate a clear decrease of the cell glycogen content while maintaining PHB level almost steady (Fig 2). 

According to activated sludge are able to accumulate large amounts of PHB when cultivated under alternation of feast and famine of external substrate (acetate). The yield of PHB production by this crdture was up to 50% of its dry weight, which is comparable with the value referred above for the cultures cultivated under microaerophilic-aerobic conditions. The influence of operating conditions, namely frequency of feeding and the ratio between the substrate and initial biomass concentration on PHA production was evaluated. The quality of polymer produced under these conditions was not determined. 

Shimizu, H., Tamura, S., Shioya, S. and Suga, K., 1993, Kinetic study of poly-D(-)-3-hydroxybutyric acid (PHB) production and its molecular weight distribution control in a fed-batch culture of Alcaligenes eutrophus. J. Ferment. Bioeng., 76 465-469. 

The isolation of thermophilic bacteria capable of producing PHA was discovered by Xu and co-workers [32], The PHB-accumulating bacterium Chelatococcus daeguensis TADl was isolated from the biofilm of a biotrickling filter, used for the removal of nitrogen oxides it was found that PHB production was growth associated and PHB... 

Yilmaz M, Soran H, Beyatli Y (2005) Determination of poly-P-hydroxybutyrate (PHB) production by some Bacillus spp. World J Microbiol Biotechnol 21 565-566 Zhao HY, Li HM, Qin LF, Wang HH, Chen G-Q (2007) Disruption of the polyhydroxyalkanoate synthase gene in Aeromonas hydrophila reduces its survival ability under stress conditions. FEMS Microbiol Lett 276 34-41... 

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