Effect of Fatty Acids on Cell Growth and PHA Accumulation

2 Effect of Fatty Acids on Cell Growth and PHA Accumulation 

It was found that, cell growth was inhibited when shorter chain length fatty acids such as caproic acid (6C) and caprylic acid (8C) were used as the sole carbon source (Iram and Cronan 2006). Earlier report by Kahar et al. suggested that C. necator favored fatty acids such as palmitic acid (C16 0), oleic acid (C18 l), and linoleic acid (C18 2). In contrast, linolenic acid (C18 3) was poorly consumed by the bacterium (Kahar et al. 2004). In addition, the residual fatty acids from soybean oil in culture medium was confirmed with thin layer chromatography (TLC) and it was observed that only certain fatty acids were utilized for cell growth and PHA accumulation. This might be due to the accumulation of linolenic acid in the culture medium which had limited the transfer of fatty acids into cells. This was 

3 Plant Oils and Agricultural By-Products as Carbon Feedstock for PH A Production 

Crude pahn kernel oil (CPKO) which is derived from the kernel of the oil palm fruit consists of large amounts of saturated fatty acids such as lauric acid (C12 0) [ 48 %], myristic acid (C14 0) [ 16 %], and palmitic acid (C16 0) [ 8 %] (Loo et al. 2005). However, the concentration of unsaturated fatty acids such as linoleic (C18 2) [ 2 %] is very low. It contrast, palm oil products derived from mesocarp such as crude palm oil (CPO) and palm olein (PO) are mainly composed of C16 0 and contain more unsaturated fatty adds such as oleic acid (C18 l), (C18 2) and trace quantities of Hnolenic add (C18 3) (Loo et al. 2005). Compared to palm oil products, soybean oil is rich in unsaturated fatty adds with C18 2 (54 %), C18 l (22 %), and C18 3 (8 %) as the major constituents while 10 % of the distributions are contributed from saturated fatty adds (Kahar et al. 2004 Loo et al. 2005). Nevertheless, soybean oil has proven to be a good carbon source for high cell density cultures. Since, CPKO contains lesser unsatuiated fatty adds, it conld become potential carbon feedstock for high cell density PHA prodnction. 

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