Phenol is a toxic compound that may be transformed into non-toxic compounds by the activity of microbial cells. The possibility of using biotransformation method for the degradation of phenol was studied using the whole cells of Rhodococcus UKMP-5M suspended in 250 mL shake flask with buffered liquid containing phenol. The cells of Rhodococcus UKMP-5M were produced by cultivation in Minimal Salt Medium (MSM) with the addition of phenol and/or glucose as carbon source. The biotransformation conditions to obtain the highest percentage of phenol degradation were as follows; pH 7.4, 0.5 g/L phenol in MSM as biotransformation medium, cells were produced by cultivation in MSM supplemented with 0.5 g/L phenol and the optimal cell concentration was 10%. The phenol degradation rate obtained in biotransformation using Rhodococcus UKMP-5M cells correlated well with phenol hydroxylase activity. The highest percentage of phenol degradation in biotransformation using suspended cells of Rhodococcus UKMP-5M was only up to 89%, which was slightly lower than those obtained in growing cell system (98%).
Environmental concern over discharge of waste cooking oil (WCO) has been on the rise. This is particularly alarming since the chain of fast food restaurants in Malaysia is thriving and therefore escalate the usage of cooking oil. Therefore, there is a challenge to manage the abundance of WCO generated by this industry. Interestingly, WCO presents as economical and readily available substrate for the conversion to biodiesel and surplus of crude glycerol which has numerous applications particularly in the food industry to manufacture artificial sweetener. However, concern arises among the Muslim populations on the source of enzyme lipase which is applied for the conversion of WCO to glycerol since the commercially available lipase for this purpose often originates from porcine. Therefore, the present study embarks on the concept of sustainability by converting waste cooking oil by halal microbial lipase to glycerol. Lipase from Rhodococcus sp. strain NAM81 demonstrated high affinity towards the substrate (Km = 1.9349 % (v/v)) and accelerated the rate of olive oil conversion (Vmax = 0.602 mU/mg/hour). The findings of WCO conversion by lipase was comparable to positive control using chemical oxidation indicating the applicability of the enzyme in industry. Therefore, production of high titre of rhodococci lipase will be attempted for future study.
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