Yu J
Department of Chemical Engineering, Hong Kong University of Science & Technology, Clear Water Bay, Sai Kung, Hong Kong, People's Republic of China.
J Biotechnol. 2001 Mar 30;86(2):105-12. doi: 10.1016/s0168-1656(00)00405-3.
Polyhydroxyalkanoate (PHA) was produced from a starchy wastewater in a two-step process of microbial acidogenesis and acid polymerization. The starchy organic waste was first digested in a thermophilic upflow anaerobic sludge blanket (UASB) reactor to form acetic (60-80%), propionic (10-30%) and butyric (5-40%) acids. The total volatile fatty acids reached 4000 mg l(-1) at a chemical oxygen demand (COD) loading rate of 25-35 g l(-1) day(-1). A carbon balance indicates that up to 43% of the organic carbon in the starchy waste went to the organic acids and the rest to biogas, volatile suspended solids and residual sludge accumulated in the reactor. The acid composition profile was affected by COD loading rate: a medium rate around 9 g l(-1) day(-1) gave a high propionic acid content (29% wt) and a high rate around 26 g l(-1) day(-1) led to a high butyric acid content (34% wt). The acids in the effluent solution after microfiltration were utilized and polymerized into PHA by bacterium Alcaligenes eutrophus in a second reactor. Fifty grams of PHA was produced from 100 g total organic carbon (TOC) utilized, a yield of 28% based on TOC, which is comparable with 55 g PHA per 100 g TOC of pure butyric and propionic acids used. PHA formation from individual acids was further investigated in a semi-batch reactor with three acid feeding rates. With a limited nitrogen source (80-100 mg NH(3) per liter), the active biomass of A. eutrophus, not including the accumulated PHA in cells, was maintained at a constant level (8-9 g l(-1)) while PHA content in the cell mass increased continuously in 45 h; 48% PHA with butyric acid and 53% PHA with propionic acid, respectively. Polyhydroxybutyrate was formed from butyric acid and poly(hydroxybutyrate-hydroxyvalerate) formed from propionic acid with 38% hydroxyvalerate.
聚羟基脂肪酸酯（PHA）由淀粉废水通过微生物产酸和酸聚合两步法制备。淀粉质有机废物首先在嗜热上流式厌氧污泥床（UASB）反应器中消化，形成乙酸（60 - 80%）、丙酸（10 - 30%）和丁酸（5 - 40%）。在化学需氧量（COD）负荷率为25 - 35 g l⁻¹ day⁻¹时，总挥发性脂肪酸达到4000 mg l⁻¹。碳平衡表明，淀粉质废物中高达43%的有机碳转化为有机酸，其余转化为沼气、挥发性悬浮固体和反应器中积累的剩余污泥。酸组成分布受COD负荷率影响：约9 g l⁻¹ day⁻¹的中等负荷率产生高含量的丙酸（29% wt），约26 g l⁻¹ day⁻¹的高负荷率导致高含量的丁酸（34% wt）。微滤后流出液中的酸在第二个反应器中被嗜碱产碱杆菌利用并聚合成PHA。利用100 g总有机碳（TOC）生产了50 g PHA，基于TOC的产率为28%，这与使用每100 g TOC的纯丁酸和丙酸生产55 g PHA相当。在具有三种酸进料速率的半间歇反应器中进一步研究了由单一酸形成PHA的情况。在有限的氮源（每升80 - 100 mg NH₃）下，嗜碱产碱杆菌的活性生物质（不包括细胞内积累的PHA）保持在恒定水平（8 - 9 g l⁻¹），而细胞质量中的PHA含量在45小时内持续增加；分别为含丁酸的48% PHA和含丙酸的53% PHA，其中含38%羟基戊酸的聚（3 - 羟基丁酸 - 羟基戊酸）由丙酸形成。聚羟基丁酸由丁酸形成。
