Growth behaviour of commercial baker’s yeast and biotransformation of chiral 2,6,6-trimethylcyclohex-2-ene-1,4-dione into its corresponding chiral precursors
Tujuan projek ini adalah untuk mengkaji kesan kepekatan substrat ke atas pertumbuhan ibu roti komersial, S. cerevisiae dan biotransformasi 2,6,6-trimethylcyclohex-2-ene-1,4-dione (ketoisophorone) mengguna sel keseluruhan S. cerevisiae. Biotransformasi fasa cecair telah dijalankan dalam kultur kelalang goncang pada pH 6.5, 35 ℃ dan 150 r.p.m. selama 52 jam. Substrat (ketoisophorone) perencatan didapati berlaku di bawah kepekatan awal substrat tertinggi, iaitu 7 g/L. Ketoisophorone dipercayai bertoksik kepada S. cerevisiae. Oleh itu, kepekatan awal substrat optimum dicadangkan sebagai 5 g/L, di mana kadar pengurangan substrat adalah tertinggi pada 0.120 g/L.hr. Pemalar kinetik Michaelis-Menten, Vmax dan Km yang ditentukan dari eksperimen dalam kelalang goncang adalah 0.180 g/L.hr dan 2.569 g/L. Akhirnya, disebabkan persaingan antara enzim-enzim, hanya ikatan kembar C=C dapat diturunkan oleh reduktase enoate (OYE), manakala penurunan karbonil yang mempunyai kadar tindak balas yang lebih perlahan tidak dapat dilakukan oleh enzimnya.
_______________________________________________________________________________________________________
The aims of this project were to study on the effect of different substrate concentrations on growth of commercial baker’s yeast, S. cerevisiae and the biotransformation of 2,6,6-trimethylcyclohex-2-ene-1,4-dione (ketoisophorone) in whole cell culture of S. cerevisiae. The liquid phase biotransformation was carried out in shake-flask culture at pH 6.5, 35 ℃ and 150 r.p.m. for 52 hours using growing cells. It was found that substrate (ketoisophorone) inhibition occurred under the highest initial substrate concentration, 7 g/L. Ketoisophorone was believed to be toxic towards S. cerevisiae. Hence, the optimum initial substrate concentration was suggested to be 5 g/L, where the rate of substrate reduction was highest at 0.120 g/L.hr. The Michaelis-Menten kinetic constants of Vmax and Km were determined from the shake-flask experiments to be 0.180 g/L.hr and 2.569 g/L, respectively. Due to the competition of co-enzymes, only C=C double bond was reduced by enoate reductase (OYE), while carbonyl reduction which has a slower reaction rate was not able to be performed by its corresponding enzyme.
Growth behaviour of commercial baker’s yeast and biotransformation of chiral 2,6,6-trimethylcyclohex-2-ene-1,4-dione into its corresponding chiral precursors
Growth behaviour of commercial baker’s yeast and biotransformation of chiral 2,6,6-trimethylcyclohex-2-ene-1,4-dione into its corresponding chiral precursors / Wong Kuan Hwa