Microbial production of polyhydroxybutyrate, a biodegradable plastic using agro-industrial waste products.

Alyaa Hamieh*, Zakia Olama and Hanafi Holail

BAU, Debbiye, Lebanon

*Corresponding Author’s E-mail: zakia.olama@bau.edu.lb  

Accepted 24 February, 2013

Abstract

Plastics produced from petrochemical sources and known as polypropylene are now accumulating in our environment at rates of millions of tons per year creating severe problems. The  present study aims to the production and isolation of  PHB (polyhydroxy-buty rate ), a biodegradable plastic, from agro-industrial waste products (whey and date molasses) due to its high economic and industrial importance , taking into consideration many points that lead to produce PHB on large scale. The methodology of this study includes screening study for the isolation of a promising microbial producer of PHB , and optimization experiments to evaluate the best environmental and physiological factors that lead to maximum PHB production. Under the optimized conditions, Lactobacillus acidophilus has shown maximum production when grown for 4 days on date molasses supplemented with NB yielding 0.412g/50ml of PHB, followed by Bacillus thuringiensis (0.367g/50ml) grown for 4 days on the same medium, and Bacillus subtilis (0.337g/50ml) grown for 6 days on whey supplemented with glucose, yeast extract, and peptone. Eleven nutritional factors were examined for their significance on PHB production using a statistical design known as Plackette-Burman. Maximum PHB output of 43.1 g/l produced by Lactobacillus acidophilus was revealed by the statistical design, which represents about 7.04 fold increase in PHB production. Fed-batch fermentation was carried out using the optimized fermentation medium and PHB production has been increased to 27.5% as compared with batch closed process. PHB was detected by transmission electron microscopy and monitoring UV spectra of the sample by scanning the samples between 220 and 300nm compared with standard PHB. Lactobacillus acidophilus can be used for PHB production on large industrial scale, solving by this one of the problems of solid waste management that results from the accumulation of plastics and saving the environment from additional air pollution caused by its recycling.

Keywords: Microbial production, polyhydroxybutyrate, agro-industrial waste products.

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