Abstract
Polyhydroxybutyrate (PHB) was produced by Cupriavidus necator CCGUG 52238 using organic acids from fermented kitchen waste. HPLC and nuclear magnetic resonance (NMR) analyses revealed that the acid comprised mainly of lactic and acetic acids. In shake flask culture, the lactic acid concentration above 10 g/L inhibited both cell growth and polyhydroxybutyrate (PHB) production. The PHB production by the strain was achieved at the highest PHB content of 52.79% in batch fermentation using the kitchen-waste derived organic acids. The PHB yield and productivity were 0.38 g/g and 0.065 g/L/h, respectively. In fed-batch culture, about 4-fold increase in PHB productivity (0.242 g/L/h) was achieved by applying intermittent feeding strategy. Key words: Cupriavidus necator CCGUG 52238, kitchen waste, organic acids, polyhydroxybutyrate (PHB).
Highlights
The growing interest in the development of biodegradable plastics with properties similar to synthetic thermoplastics for the management of the existing plastic waste has directed the attention towards bacterial polyhydroxyalkanoates (PHA)
Reported value of 4.6 and 5.1 by Kim et al (2004) and Stabnikova et al (2008), respectively. This is due to the action of indigenous microbes in the fermented kitchen wastes that break down the complex organic materials into organic acids and contributed to the acidity of the solution
The concentrated organic acid was brown in colour and was consisted of 210 g/L lactic acid and 13.9 g/L acetic acid
Summary
The growing interest in the development of biodegradable plastics with properties similar to synthetic thermoplastics for the management of the existing plastic waste has directed the attention towards bacterial polyhydroxyalkanoates (PHA). As of 2008, 23,000 tonnes of waste is produced each day in Malaysia, the generation in Kuala Lumpur alone accounted to 3,000 tonnes per day. This will continue to increase in coming years and is expected to reach 30,000 tons per day in 2020 (GEC). While composting the kitchen refuse can recycle back the nutrients and energy to soil and reduce almost 50% of the waste; anaerobic digestion can be applied to convert the food waste into organic acids which are preferable substrate for PHA production. Producing PHAs from kitchen waste can further reduce the inevitable usage of conventional plastics when biodegradable PHA as packaging material would take place in the market
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