1、聚羥基烷酸脂論文：兩段式和三段式工藝制取聚羥基烷酸酯的試驗研究【中文摘要】聚羥基烷酸酯(PHA)是一類羥基脂肪酸的聚合物,當外界環境較惡劣時,部分微生物可以在體內以內碳源的形式貯存PHA。PHA具有生物相容性和可生物降解性,同時根據單體組分的不同還可以具有同石化塑料相類似的多種物理性質,可以代替現行的難降解塑料,以此可緩解環境固體廢棄物污染。然而目前PHA商業化生產都采用純菌發酵的方式,成本較高,阻礙了PHA的大規模應用。采用活性污泥混合菌群生產PHA可以采用廉價的有機廢物為底物,有望大大降低PHA的生產成本。兩段式PHA生產工藝包括有機廢物厭氧酸化和PHA生產兩步,后者在時間上分為污泥適應階

2、段和PHA積累階段,適應階段采用均衡營養比例而PHA積累階段則限制進水中營養元素。本研究發現在PHA積累階段一步減少進水中80%(相對于均衡比例)的氨氮,比逐步減少可以更有效的促進PHA積累;在每周期底物都可以消耗完畢的條件下,無論底物為乙酸鈉還是污泥水解液,該階段反應器厭氧-好氧運行與好氧運行得到的結果幾乎沒有區別;研究還發現適應期污泥齡較長時可以保證反應器長時間的穩定運行,而污泥齡較短時易引發污泥膨脹,污泥齡低于5天引發的污泥膨脹會使得污泥產PHA能力下降。以污泥水解液為底物時,其中VFAs可以得到的快速的吸收,PHA積累與其中氨氮水平有很大關系。三段式PHA生產工藝包括有機廢物厭氧酸化、

3、菌群富集和PHA積累,其中菌群富集是最重要的一步。本研究以乙酸鈉為底物考察以SBR富集產PHA菌群時,發現反應器易于發生污泥膨脹。在污泥齡為1天、底物負荷較高(6.6 g COD/L/d)時,反應器膨脹非常嚴重,大量泡沫產生,污泥很快喪失了產PHA能力;而污泥齡為10天、負荷較低(2.7 g COD/L/d)條件下得到的膨脹污泥則具有較高的PHA合成能力,好氧SBR運行102天時污泥積累PHA最大含量達到了53%,PHA平均積累速率為0.19 mg COD/mg X/h,PHA產率為0.76 mg COD/mg COD,而與此SBR同步運行的厭氧-好氧SBR則運行55天左右后突然崩潰,污泥濃度

4、甚至不足500 mg/L。以蔗糖模擬糖蜜廢水經厭氧酸化用于PHA合成時,產酸反應器啟動運行1個月后逐漸穩定為乙醇型發酵,此時出水經中空纖維膜過濾后用于SBR富集產PHA混合菌群和PHA積累,實現了生物制氫與PHA合成系統的耦合。SBR運行負荷為4.2-4.5 g COD/L/d,污泥齡為10天,啟動運行1個月內污泥濃度從3300 mg/L增大到8000 mg/L以上,盡管底物充盈時溶解氧控制于3.0 mg/L左右,然而30天時SBR依然發生了污泥膨脹,這可能是污泥濃度過大導致的。對比發現,膨脹后的污泥在底物吸收、PHA合成以及生長方面比非膨脹污泥快了1倍左右。本實驗在SBR運行25天時,系統每

5、消耗1 kg COD的蔗糖,約生產16 L氫氣和0.1 kg COD的PHA,其中單體HV質量比約占24%左右?！居⑽恼縋olyhydroxyalkanoates (PHAs) are a class of polymers, which can be accumulated as internal carbon sources by part microorganisms under adverse circumstances. PHAs are biocompatible and biodegradable and can also possess the similar proper

6、ties with the petro made plastics, which enables them to substitute the current plastics to reduce solid wastes. However, PHAs in market are all commercially produced by pure cultures, which bring about high costs and hampered their large-scale application. PHA production by mixed microbial cultures

7、 can be completed in open reactors and future more, more cheap organic wastes can be used. This would make cost reduction possible.Two-stage PHA production process includes acidogenic fermentation of organic wastes and PHA production, and the latter is composed by sludge acclimation and PHA accumula

8、tion. In sludge acclimation, nutrients are balanced while in PHA accumulation, nutrients are unbalanced. In this study, results showed that direct limitation of ammonia by 80% (compared with balance level) in influent could better stimulate PHA accumulation than gradual limitation. When there was no

9、 substrate left in every cycle, little difference was observed in PHA accumulation between anaerobic-aerobic and aerobic operation with substrate as acetate or sludge alkaline fermentation liquids. It can also be drawn that long sludge retention time would guarantee longterm stability of the reactor

10、, while low sludge retention time would bring about sludge bulking. Especially, when sludge retention time was lower than 5 days, the PHA storage capacity would be damaged. VFAs could be uptaken rapidly and the PHA accumulation depended highly on the level of ammonia when the substrate was sludge al

11、kaline fermentation liquids.Three-stage PHA production process includes acidogenic fermentation of organic wastes, culture selection and PHA accumulation, and stage of culture selection is the most important. It was observed that bulking sludge was easily established when selecting cultures in SBR w

12、ith actate as substrate. Under SRT of 1d and high organic loading rate (6.6 g COD/L/d), the bulking was more severe with a great deal of foam and poor PHA storage ability. While, under SRT of 10 d and low organic loading rate (2.7 g COD/L/d), bulking sludge possessed high PHA storage capacity. After

13、 102 daysoperation, sludge from SBR could accumulate PHA to 53% of TSS, under ammonia starvation, with average storage rate of 0.19 mg COD/mg X/h and yield of 0.76 mg COD/mg COD. However, another SBR operated in parallel with anaerobic-aecobic pattern suddenly failed after 55 daysoperation.When usin

14、g cane sugar to simulate molassess as the substrate, after anaerobic fermented, for PHA production, the CSTR gradually stablized towards ethonal-type fermantation one month after startup. The effluent was clarified with hollow fiber membrane and then was used for culture selection and PHA accumulati

15、on, thus coupling bio-hydrogen production with PHA production system was achieved. The TSS in SBR rised up to more than 8000 mg/L from 3300 mg/L with organic loading rate of 4.2-4.5 g COD/L/d and SRT of 10 d. Although DO was maintained above 3 mg/L in feast phase, sludge bulking still happened after

16、 30 daysoperation. This may be caused by high sludge concentration. Bulking sludge exhibited higher rates in substrate uptake, PHA storage and biomass proliferation than well-settling sludge, about 2 times than the latter. When SBR run 25 days after inoculation, the whole system could produce 16 L H

17、2 and 0.1 kg COD PHA using 1 kg COD cane sugar. The HV weight proportion of PHA was 24% approximately.【關鍵詞】聚羥基烷酸脂 混合菌群 污泥膨脹 生物制氫 PHA合成【英文關鍵詞】polyhydroxyalkanoates mixed microbial culture sludge bulking bio-hydrogen production PHA synthesis【目錄】兩段式和三段式工藝制取聚羥基烷酸酯的試驗研究摘要4-6Abstract6-7第1章 緒論11-311.1 課題背景

18、11-121.1.1 課題來源111.1.2 課題研究目的和意義11-121.2 PHA 概述12-191.2.1 PHA 結構與性質12-141.2.2 細胞儲存PHA 的微生物學意義14-151.2.3 微生物合成PHA 的代謝機制15-181.2.4 PHA 的提取回收18-191.3 混合菌群合成PHA 國內外研究現狀19-291.3.1 底物選擇19-201.3.2 工藝流程20-221.3.3 工藝運行策略22-251.3.4 影響因素25-291.4 主要研究內容29-31第2章 實驗材料與方法31-362.1 實驗裝置及運行工況31-332.1.1 實驗裝置31-322.1.2

19、 主要設備儀器32-332.2 檢測方法33-362.2.1 PHA 的檢測332.2.2 乙醇-VFAs 的檢測33-342.2.3 氣體成分檢測342.2.4 其他常規指標的測定與分析方法34-36第3章 兩段式PHA 制取工藝優化36-493.1 氨氮限制方式對PHA 積累的影響36-393.1.1 實驗工藝控制36-373.1.2 污泥性狀的變遷37-383.1.3 限制進水氨氮下PHA 的循環積累38-393.2 PHA 積累期厭氧-好氧與好氧運行方式的對比39-413.2.1 實驗工藝控制39-403.2.2 底物消耗與PHA 積累40-413.3 短污泥齡、短周期的污泥適應期41-453.3.1 實驗工藝控制423.3.2 污泥性狀的變遷42-433.3.3 底物消耗與PHA 積累43-453.4 污泥水解液用于兩段式工藝45-483.4.1 實驗工藝控制45-463.4.2 底物為污泥水解液時PHA 積累情況46-483.5 本章小結48-49第4章 以乙酸鈉為底物富集產PHA 混合菌群49-634.1 實驗工藝控制49-5