The effect of glucose concentration on the co-factor recycling in a non-growing whole-cell saccharomyces cerevisiae-mediated ketoisophorone biotransformation
Kajian ini dijalankan bagi mengkaji kesan kepekatan glukosa yang berbeza terhadap pengitaran semula co-faktor dalam sel rehat Saccharomyces cerevisiae. Selain itu, kajian ini juga mengkaji kesan kepekatan glukosa yang berbeza terhadap biotransformasi 2,6,6-trimethylcyclohex-2-ene-1,4-dione atau lebih dikenali sebagai ketoisophorone dalam sel rehat Saccharomyces cerevisiae. Biotransformasi fasa cecair dijalankan dalam kultur kelalang goncang. Keadaan kendalian biotransformasi ini ialah 37 °C, 150 rpm, 5 g/L S. cerevisiae, 0.2 g/L ketoisophorone dan kepekatan glukosa yang berbeza (5 g/L, 10g/L, 15 g/L). Dalam tindak balas ini, ketiga-tiga kepekatan glukosa menunjukkan kehadiran co-faktor. Ini menunjukkan kewujudan proses kitaran semula co-faktor dalam biotransformasi ketoisophorone. Kepekatan glukosa sebanyak 15 g/L menunjukkan nilai penyerapan yang tertinggi iaitu 0.4100. Terdapat 5.018×1022 molekul glukosa dalam kepekatan glukosa 15 g/L. Kepekatan glukosa yang optimum untuk pembentukan actinol ialah 15 g/L. Sebanyak 12 mol % actinol terhasil daripada biotransformasi yang mengunakan 15g/L kepekatan glukosa. Semasa biotransformsi ini, hanya levodione yang terhasil. Kepekatan NAD+ yang tinggi akan merencatkan alkohol dihidrogenase. Ini akan menghalang reduksi keton untuk berlaku. Tambahan pula, kadar tindak balas penurunan keton amat perlahan jika dibandingkan dengan penurunan carbon yang dihubungakan dengan ikatan kembar oleh reduktase enoate.
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The aim of this study is to investigate the effect of different glucose concentrations on the recycling of co-factor in a non-growing whole-cell Saccharomyces cerevisiae. Besides that, this study also investigates the effect of different glucose concentrations on the biotransformation of 2,6,6-trimethylcyclohex-2-ene-1,4-dione also known as ketoisophorone in a non-growing whole-cell S. cerevisiae. The liquid phase biotransformation was carried out in a shake-flask culture. The conditions of biotransformation are 37 °C, 150 rpm, 5 g/L S. cerevisiae, 0.2 g/L ketoisophorone and varied concentration of glucose (5 g/L, 10g/L, 15 g/L). It was found that level of co-factors were shown at different glucose concentrations. This indicates that co-factor recycling process exist in this reaction.15 g/L of glucose showed the highest value of absorbance which is 0.4100. 5.018×1022 number of glucose molecules are present in 15 g/L glucose. The optimum concentration of glucose for the formation of actinol is 15 g/L. 15 g/L of glucose showed a maximum of 12 mole % of actinol formed. Levodione was the only intermediate formed during the biotransformation. Ketone reduction did not occur due to the inhibition of alcohol dehydrogenase caused by high concentration of NAD+. Besides, ketone reduction has a slower reaction rate as compared to the reduction of carbon-carbon double bond by enoate reductase.
The effect of glucose concentration on the co-factor recycling in a non-growing whole-cell saccharomyces cerevisiae-mediated ketoisophorone biotransformation
The effect of glucose concentration on the co-factor recycling in a non-growing whole-cell saccharomyces cerevisiae-mediated ketoisophorone biotransformation / Nanthini Umapathy