Keenan Thomas M, Tanenbaum Stuart W, Stipanovic Arthur J, Nakas James P
Department of Environmental and Forest Biology, SUNY-College of Environmental Science and Forestry, Syracuse, New York 13210, USA.
Biotechnol Prog. 2004 Nov-Dec;20(6):1697-704. doi: 10.1021/bp049873d.
Poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (P(3HB-co-3HV)) copolymers were prepared via shake-flask fermentations of Burkholderia cepacia (formerly Pseudomonas cepacia) containing 2.2% (w/v) xylose and concentrations of levulinic acid ranging from 0.07% to 0.67% (w/v). Periodic harvest of shake-flask cultures from 48 to 92 h post-inoculation yielded 4.4-5.3 g/L of dry cell biomass, containing 42-56% (w/w) P(3HB-co-3HV), with optimal product yield occurring between 66 and 74 h. Growth and PHA accumulation enhancement were observed with concentrations of levulinic acid from 0.07 to 0.52% (w/v), producing dry cell biomass and P(3HB-co-3HV) yields of 9.5 and 4.2 g/L, respectively, at the 0.52% (w/v) concentration of levulinic acid. Representative samples were subjected to compositional analysis by 300 MHz 1H and 150 MHz 13C NMR, indicating that these random copolymers contained between 0.8 and 61 mol % 3-hydroxyvalerate (3HV). Solvent-cast film samples were characterized by differential scanning calorimetry, which demonstrated melting temperatures (Tm) to decrease in a pseudoeutectic fashion from 174.3 degrees C (0.8 mol % 3HV) to a minimum of 154.2 degrees C (25 mol % 3HV) and the glass transition temperatures (Tg) to decrease linearly from 2.1 to -11.9 degrees C as a function of increasing mol % 3HV. Thermogravimetric analysis of the copolymer series showed the temperature for onset of thermal decomposition (T(decomp)) to vary as a function of mol % 3HV from 273.4 to 225.5 degrees C. Intrinsic viscosities (eta) varied from 3.2 to 5.4 dL/g, as determined by dilute solution viscometry. Viscosity average molecular weights (Mv) of the copolymers were determined to range from 469 to 919 kDa, indicating that these P(3HB-co-3HV) copolymers are of sufficient molecular mass for commercial application.
通过含有2.2%（w/v）木糖和浓度范围为0.07%至0.67%（w/v）的乙酰丙酸的洋葱伯克霍尔德菌（原洋葱假单胞菌）摇瓶发酵制备聚（β-羟基丁酸酯-co-β-羟基戊酸酯）（P(3HB-co-3HV)）共聚物。在接种后48至92小时定期收获摇瓶培养物，得到4.4 - 5.3 g/L的干细胞生物质，其中含有42 - 56%（w/w）的P(3HB-co-3HV)，最佳产物产量出现在66至74小时之间。当乙酰丙酸浓度为0.07%至0.52%（w/v）时，观察到生长和PHA积累增强，在乙酰丙酸浓度为0.52%（w/v）时，干细胞生物质产量和P(3HB-co-3HV)产量分别为9.5和4.2 g/L。代表性样品通过300 MHz 1H和150 MHz 13C NMR进行组成分析，表明这些无规共聚物含有0.8至61 mol%的3-羟基戊酸酯（3HV）。溶剂浇铸膜样品通过差示扫描量热法进行表征，结果表明其熔点（Tm）以假低共熔方式从174.3℃（0.8 mol% 3HV）降低至最低154.2℃（25 mol% 3HV），玻璃化转变温度（Tg）随着3HV mol%的增加从2.1℃线性降低至 - 11.9℃。共聚物系列的热重分析表明热分解起始温度（T(decomp)）随3HV mol%从273.4℃变化至225.5℃。通过稀溶液粘度法测定特性粘度（η）在3.2至5.4 dL/g之间变化。共聚物的粘均分子量（Mv）测定范围为469至919 kDa，表明这些P(3HB-co-3HV)共聚物具有足够的分子量用于商业应用。
