Microbial production of polyhydroxyalkanoates by bacteria isolated from oil wastes |
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Authors: | Wong Ai Ling Chua Hong Yu Peter Hoi Fu |
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Institution: | (1) Open Laboratory of Chirotechnology and Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong;(2) Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong |
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Abstract: | A Gram-positive coccus-shaped bacterium capable of synthesizing higher relative molecular weight (M
r), polyhydroxybutyrate (PHB) was isolated from sesame oil and identified as Staphylococcus epidermidis (by Microbial ID, Inc., Newark, NJ). The experiment was conducted by shake flask fermentation culture using media containing
fructose. Cell growth up to a dry mass of 2.5 g/L and PHB accumulation up to 15.02% of cell dry wt was observed. Apart from
using single carbohydrate as a sole carbon source, various industrial food wastes including sesame oil, ice cream, malt, and
soya wastes were investigated as nutrients for S. epidermidis to reduce the cost of the carbon source. As a result, we found that by using malt wastes as nutrient for cell growth, PHB
accumulation of S. epidermidis was much better than using other wastes as nutrient source. The final dried cell mass and PHB production using malt wastes
were 1.76 g/L and 6.93% polymer/cells (grams/gram), and 3.5 g/L and 3.31% polymer/cells (grams/gram) in shake flask culture
and in fermentor culture, respectively. The bacterial polymer was characterized by 1H-nuclear magnetic resonance (NMR), 13C-NMR, Fourier transform infrared, and differential scanning calorimetry. The results show that with different industrial
food wastes as carbon and energy sources, the same biopolymer (PHB) was obtained. However, the use of sesame oil as the carbon
source resulted in the accumulation of PHB with a higher melting point than that produced from other food wastes as carbon
sources by this organism under similar experimental conditions. |
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Keywords: | Staphylococcus epidermidis polyhydroxybutyrate food wastes |
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