Effect of Organic Acid Substrates on the Composition of Poly (hydroxybutyrate-co-hydroxyvalerate) Produced by Alcaligenes eutrophus

• Main Authors: Chen,Yi - Ju, 陳怡如
• Other Authors: J. R. Too
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/62955245199434891232

碩士 === 大葉大學 === 食品工程研究所 === 89 === The bio-polymer, PHBV (poly-hydroxybutyrate-co- hydroxyvalerate), having physical properties similar to poly-propylene, is a kind of polyester produced by microorganisms. The application of PHBV is quite extensive because it is suitable for current polymer processing. Since PHBV is biodegradable, its usage is even more significant for environmental protection. The Alcaligenes eutrophus (Ralstonia eutropha) was under various time of feeding sodium propionate or valerate in order to study: the microbial growth rate, the PHBV accumulation, the consumption of carbon、nitrogen、sodium propionate and valerate substrates during fermentation. Results show that, the microbial growth rate, biomass increase and PHBV accumulation at different stage of feeding propionate and valerate from the largest to smallest have the order of later, middle and early. The order of the mass fraction in biomass from high to low is early, middle and later stage when the propionate was fed. For the valerate case , early stage is the highest, and the middle and the later stage are about the same. Therefore, feeding propionate or valerate at the early stage can produce a PHBV product with a higher HV mole fraction . For the carbon sources,average specific glucose and propionate consuming rates were explored. The specific consuming rate is the substrate consumption per unit residual biomass within a unit time. The specific consuming rate is the substrate consumption per unit residual biomass within a unit time. The average specific consuming rate of propionate fed at an early stage is the highest, and the PHBV has the highest HV mole fraction and the average specific PHV production rate is the highest for this stage The mass fraciotn of PHBV in biomass among three stages has no substantial defference. All of them contain about 58% PHBV, but higher than those of feeding propionate. The HV:HB mole ratio in PHBV, just like the case of feeding propionate, is the highest when the valerate was fed at an early stage (HB:HV = 0.23 : 0.77) ; while the middle and the latter stages have no substantial difference (about 0.76:0.24). The order of average specific carbon source (glucose and valerate) consuming rates is later＞middle＞early . The specific microbial growth rates are early〈middle〈later. This may suggest that organic acidic substrates such as propionate and valerate are toxic to Alcaligenes eutrohus.