Enhanced Production Of Poly (3-Hydroxybutyrate-Co-4-Hydroxybutyrate) With High 4hb Unit Composition Using Transformant Cupriavidus sp.USMAA1020
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Date
2017-03
Authors
Hambali, Norhafini
Journal Title
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Publisher
Universiti Sains Malaysia
Abstract
Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] copolymer is one of emerging biopolymer which possess suitable properties to be applied in medical applications. P(3HB-co-4HB) with high 4HB unit is favorable as this enhance the biocompatibility and mechanical properties of this copolymer as implantable and absorbable biomaterial. However, biosynthesis of P(3HB-co-4HB) in single-stage cultivation produces low 4HB unit composition with low productivity. Cupriavidus sp. USMAA1020, a bacterium isolated from Malaysian environment, was capable to synthesize P(3HB-co-4HB) with different 4HB unit compositions but only to a maximum of 70 mol% through single-stage cultivation. The present work studied the ability of transformant Cupriavidus sp. USMAA1020 which has additional PHA synthase gene, phaC of wild-type strain Cupriavidus sp. USMAA2-4 to produce P(3HB-co-4HB) with 4HB unit composition more than 80 mol%. With the presence of the extra PHA synthase gene, phaC, which was expressed heterologously, this strain was found to accumulate high PHA accumulation of 69 wt% with 86 mol% of 4HB unit composition in shake flask cultivation using mixed substrate of 1,6-hexanediol and 1,4-butanediol. Single-stage cultivation in 3 L fermentation confirmed the ability of this strain to produce high 4HB unit composition of 95 mol% with 75 wt% PHA content and high PHA concentration of 18.7 g/L. Interestingly, this strain was also found capable of surviving high carbon concentration (1.05 wt% C) better than the wild-type strain (0.69 wt% C).
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Keywords
Production of poly (3-hydroxybutyrate-co-4-hydroxybutyrate) , using transformant cupriavidus sp.USMAA1020