Tujuan kajian ini adalah untuk mengkaji kesan biotransformasi 2,6,6-trimethylcyclohex-2-ene-1,4-dione (ketoisophorone), 2,6,6-trimethylcyclohexane-1,4-dione [(6R)-levodione] dan 4-hydroxy-2,6,6-trimethylcyclohex-2-en-1-one [(4S)-phorenol] ke atas pertumbuhan yis komersial, Saccharomyces cerevisiae dan biotransformasi ketoisophorone dengan menggunakan sel keseluruhan S. cerevisiae. Biotransformasi fasa cecair telah dijalankan dalam kultur kelalang goncang pada pH 6.5, 37 ℃ dan 150 r.p.m dengan menggunakan S. cerevisiae. Persamaan logistik telah digunakan untuk sesuaikan dengan data eksperimen yang diperolehi daripada penapaian kumpulan S. cerevisiae. Kadar pertumbuhan diperolehi daripada penapaian S. cerevisiae tanpa substrat adalah 0.034 hr-1. Ketoisophorone, (6R)-levodione dan (4S)-phorenol dipercayai bertoksik kepada S. cerevisiae. Denagan wujudnya ketoisophorone, (6R)-levodione dan (4S)-phorenol, kadar pertumbuhan masing-masing telah dikurangkan kepada 0.0266 hr-1, 0.024 hr-1 dan 0.0255 hr-1. Akhir sekali, laluan biotransformasi ketoisophorone dengan menggunakan S. cerevisiae telah dicadangkan dalam kajian ini. Disebabkan persaingan antara enzim-enzim dan kadar tindak balas pengurangan ikatan kembar karbon-karbon yang lebil tinggi daripada kadar tindak balas pengurangan karbonil, kepekatan (6R)-levodione yang lebih tinggi telah timbul sepanjang reaksi yang berpanjangan berbanding dengan kepekatan (4S)-phorenol.
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The aim of this research is to study the effect of 2,6,6-trimethylcyclohex-2-ene-1,4-dione (ketoisophorone), 2,6,6-trimethylcyclohexane-1,4-dione [(6R)-levodione] and 4-hydroxy-2,6,6-trimethylcyclohex-2-en-1-one [(4S)-phorenol] on the growth of commercial baker’s yeast, S. cerevisiae and the biotransformation of ketoisophorone in whole-cell of Saccharomyces cerevisiae. The liquid-phase biotransformation was carried out in shake-flask culture at pH 6.5, 37 ᵒС and 150 r.p.m utilizing growing cells of S. cerevisiae. The logistic equation was employed to fit the experimental data obtained from the batch fermentation of S. cerevisiae. The specific growth rate obtained from the fermentation of S. cerevisiae where the substrate is absent was 0.034 hr-1. Ketoisophorone, (6R)-levodione and (4S)-phorenol were believed to be toxic towards S. cerevisiae. With the presence of ketoisophorone, (6R)-levodione and (4S)-phorenol, the specific growth rate have reduced to 0.0266 hr-1, 0.024 hr-1 and 0.0255 hr-1 respectively. Biotransformation route of ketoisophorone by growing cells was proposed from the study. Due to the competition of co-enzymes and higher reaction rate of carbon-carbon double bond reduction compared to the reaction rate of carbonyl reduction, higher concentration of (6R)-levodione arose along the prolonged reaction compared to the concentration of (4S)-phorenol.
Baker’s yeast mediated biotransformation of 2,6,6-trimethylcyclohex-2-ene-1,4-dione into its corresponding synthons / Wong Kang Choon