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嗜盐混合菌发酵生产聚羟基脂肪酸酯(polyhydroxyalkanoate,PHA)具有免灭菌程序、产量高、易提取等优势而被广泛关注。集中考察了pH对嗜盐混合菌(MMCs)发酵混合挥发性有机酸(VFA)生产PHA的影响。研究结果表明,在6.5~8.2范围内pH对PHA合成没有明显影响,过高或者过低的pH都会降低PHA合成速率和VFA的吸收速率。发酵体系的pH影响了嗜盐MMC的PHA产量,但是在酸性和碱性条件下却存在不同的影响机制。碱性环境增大了VFA的解离程度,导致MMC对底物的吸收耗费大量的能量,造成VFA吸收速率的下降。这一作用在pH升高至9.2以上时表现显著。酸性环境下,分子态VFA进入细胞后改变了胞内的pH,降低了相关酶和蛋白质的活性,从而影响了底物的利用。当pH=5.2时微生物代谢及底物利用能耗量降低,导致PHA胞内降解利用率降低,刺激了PHA合成量的提高。PHA组分受pH影响不大,初始pH=5.2~10.2时羟基脂肪酸戊酯(hydroxyvalerate,HV)所占比例维持在34.9%~38.3%范围内。本研究对于进一步利用嗜盐MMC发酵含有混合VFA的废弃物生产PHA具有重要的指导意义。 相似文献
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本文研究了黑曲霉在以淀粉为原料的发酵培养基上发酵生产枸橼酸的工艺,探讨温度、时间、pH值、溶氧等因素对产酸的影响,分析得到最佳的反应条件是黑曲霉在发酵培养基中当温度是36℃,PH值介于2.0-2.5,摇床转速220转/分,发酵时间72h,产枸橼酸的效率和量达到最佳。 相似文献
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挥发性脂肪酸(VFA)是污水生物处理中反硝化脱氮和厌氧释磷过程必需的碳源,还能作为底物生产高附加值的产品,而利用剩余污泥进行厌氧发酵是产VFA的重要途径之一。为了提高污泥产酸效率,利用外源添加剂促进和强化污泥厌氧发酵产酸的研究逐渐引起重视。文章总结了抗生素、表面活性剂、植物化学物质和盐类四类外源添加剂对污泥厌氧发酵产酸过程的影响,分别从外源添加剂对污泥的增溶、水解、产酸和产甲烷四个过程进行了分析,同时阐述了外源添加剂在污泥中的降解、残留状况,最后提出对两种或两种以上的外源添加剂联用促进产酸和寻找能促进污泥产酸的共发酵基质也是今后的研究重点。 相似文献
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《应用化工》2022,(2):326-330
通过单基质发酵实验研究了不同种类的泔脚废油脂对厌氧发酵产奇数碳挥发性脂肪酸(OCFA)的影响,考察了泔水浮油、废弃肥肉及煎炸废油中VFAs浓度的变化规律。结果表明,在反应过程中,泔水浮油VFAs浓度的增长速率高达1 152 mg/(L·d),能在单位时间内获得最大VFAs浓度6 430.22 mg/L;基于营养物质、微生物、脂肪等含量的差异,废弃肥肉产OCFA浓度和OCFA/VFAs的比例最大,为3 356.47 mg/L、66%,相较于泔水浮油和煎炸废油,OCFA浓度分别增长了29%,33%,OCFA、VFAs分别增长了29%,3%。因此,废弃肥肉可作为探讨提高OCFA产率的优质发酵原料;此外,油脂的抑制效果对泔水浮油作用较小,而使得废弃肥肉和煎炸废油的VFAs浓度增长、产酸滞后等。 相似文献
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以木薯酒精废水为碳源,通过批次实验研究了亚硝酸盐对厌氧产酸耦合反硝化系统的影响。结果表明,投加600 mg·L-1 3NO-N-后的最终产酸量与空白反应器相差不大,但是投加相同浓度亚硝酸盐后产酸受到严重抑制,最终产酸量仅为空白反应器的1.8%。而硝酸盐还原过程中厌氧产酸受到抑制可能是由于反硝化中间产物亚硝酸盐的存在,低投加量的亚硝酸盐即可对厌氧产酸产生强烈的抑制作用并具有持续性,且对各产酸组分的影响作用:正丁酸丙酸乙酸。随着2COD/NO-N-的降低,亚硝酸盐的还原率由74.9%降低至22.2%。当游离亚硝酸(free nitrous acid,FNA)浓度为0.05 mg·L-1以上时,亚硝酸盐还原几乎被完全抑制(90%以上)。此外,随着2COD/NO-N-的增加,反硝化所占的比例逐渐减小,而DNRA过程(dissimilatory nitrate reduction to ammonium,异化硝酸盐还原为铵)逐渐占优势。 相似文献
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以木薯酒精废水为碳源,通过批次实验研究了亚硝酸盐对厌氧产酸耦合反硝化系统的影响。结果表明,投加600 mg·L-1 后的最终产酸量与空白反应器相差不大,但是投加相同浓度亚硝酸盐后产酸受到严重抑 制,最终产酸量仅为空白反应器的1.8%。而硝酸盐还原过程中厌氧产酸受到抑制可能是由于反硝化中间产物亚硝酸盐的存在,低投加量的亚硝酸盐即可对厌氧产酸产生强烈的抑制作用并具有持续性,且对各产酸组分的影响作用:正丁酸>丙酸>乙酸。随着 的降低,亚硝酸盐的还原率由74.9%降低至22.2%。当游离亚硝酸(free nitrous acid, FNA)浓度为0.05 mg·L-1以上时,亚硝酸盐还原几乎被完全抑制(90%以上)。此外,随着 的增加,反硝化所占的比例逐渐减小,而DNRA过程(dissimilatory nitrate reduction to ammonium,异化硝酸盐还原为铵)逐渐占优势。 相似文献
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Panagiotis Elefsiniotis William K. Oldham 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,60(1):89-96
This study explored the effect of pH on the acid-phase anaerobic digestion of primary sludge. Controlled and uncontrolled pH experiments were conducted using two bench-scale, continuous-flow reactors having different configurations: a completely mixed reactor (CMR) with clarifier and solids recycling, and an upflow anaerobic sludge blanket (UASB) unit. Results indicate that the specific rates of VFA production and COD solubilization, in either system, were not affected by the variation in pH between 4·3 and 5·2, but at higher pH values (5·9–6·2) a significant decline (by 25–30%) in both parameters was observed. Analysis of the degradation behavior of the three important organic classes (carbohydrates, proteins, and lipids) revealed that each class followed an individual trend with respect to pH changes. Acetic acid was the major end-product of acidogenic digestion in both reactors, regardless of pH. The percent VFA distribution did not appear to be influenced by pH variation, except for propionic and butyric acids. Besides VFAs, small amounts of formic acid, ethanol, and lactic acid were also formed at all pH values tested. 相似文献
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以玉米秸秆为原料,先经复合菌系进行好氧生物预处理,然后接种厌氧污泥进行厌氧发酵,考察了预处理时间对厌氧发酵的影响,并测定木质纤维素结构及含量变化、关键性酶活、微生物多样性和厌氧发酵酸化产量。研究结果表明:随着预处理时间的延长,玉米秸秆的结构逐渐被破坏,木质素过氧化物酶活性逐渐降低,木聚糖酶和纤维素酶活性逐渐升高,最高分别达0.879和0.025 7 U/mg。放线菌、芽孢杆菌和曲霉菌是秸秆好氧生物预处理中的优势菌群。玉米秸秆经好氧生物预处理2 d,厌氧发酵产酸效果最佳,乙醇和挥发性脂肪酸产量为249.3 mg/g,比未处理提高了46.73%;玉米秸秆经好氧生物预处理5 d,乙醇和挥发性脂肪酸产量为138.2 mg/g,比未处理降低了18.66%。过长的玉米秸秆好氧预处理时间会使玉米秸秆中半纤维素、纤维素过度降解,这是造成玉米秸秆厌氧发酵产酸量下降的主要原因。以能源化、资源化为目的的玉米秸秆厌氧发酵预处理时,利用复合菌系好氧生物处理作为其预处理方法,应严格控制预处理时间,避免因为纤维素、半纤维素过度降解导致的产品产率下降问题。 相似文献
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Volatile fatty acids production from cheese whey: influence of pH,solid retention time and organic loading rate
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Rolando Rafael Calero Borja Lagoa‐Costa María Mercedes del Coro Fernandez‐Feal Christian Kennes Maria Carmen Veiga 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2018,93(6):1742-1747
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Burak Demirel Orhan Yenigun 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(7):755-760
The performance of a laboratory‐scale mesophilic acidogenic reactor was evaluated in this study, in terms of volatile fatty acid production and distribution, with respect to variations in hydraulic retention time (HRT). The continuous flow‐completely mixed anaerobic reactor, coupled with a conventional gravity settling tank and a continuous recycling system, was operated in a hydraulic retention time ranging between 24 and 12 h, and up to an organic loading rate of about 9.3 kg COD m?3 d?1, without pH control. The acid production gradually increased proportionally to the organic loading rate, with decrease in hydraulic retention time. The highest degree of acidification and the rate of acid production were 56% and 3.1 g dm?3 d?1 at 12 h of HRT. Variations in hydraulic retention time affected volatile fatty acid production and distribution substantially, for the range investigated. Acetic, propionic, butyric and valeric acids were commonly produced during acidogenesis of dairy wastewater. Copyright © 2004 Society of Chemical Industry 相似文献
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Tween80对稻草水解及同步糖化与发酵产乳酸的影响 总被引:2,自引:0,他引:2
在生物转化纤维原料产乳酸的过程中,酶解纤维原料产还原糖是限速步骤。为了获得较高的产物产率,需较高的酶用量,这使大规模酶解废弃纤维原料的成本很高。对吐温80在酶解稻草纤维素产糖,以及耐高温乳酸菌同步糖化发酵稻草产乳酸过程中的作用进行了考察。初步结果表明,吐温80加入可使保持同等程度的水解率所需的酶用量降低,添加0.2 g/g底物的吐温80到酶用量10 FPU/g体系,水解120 h的糖产率为292.2 mg/g,比不加表面活性剂体系的糖产率增加了11%;添加0.7 g/L的吐温80进行同步糖化与发酵72 h,能使乳酸产量提高24.2%。 相似文献
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以苯酚为液化剂,甘油为辅助液化剂,在浓硫酸催化作用下对水稻秸秆进行微波液化。分别研究了液化条件对液化残渣率的影响,并通过单因素试验和正交试验得出最佳反应条件:即在微波功率500 W,液固比为7:1,m(苯酚):m(甘油)为4:1,浓硫酸用量为5%,150 ℃,反应时间22.5 min,所得残渣率最小,为7.17%。凝胶渗透色谱结果显示随着液化时间的延长,液化产物的相对分子质量出现逐渐减小的趋势,而分散系数则略增大。通过液化产物的红外光谱分析发现,纤维素和半纤维素较易降解,液化残渣主要成分是木质素及其衍生物。 相似文献
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Wilson Parawira Marika Murto John S Read Bo Mattiasson 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(7):673-677
The production of volatile fatty acids by anaerobic digestion of solid potato waste was investigated using a batch solid waste reactor with a working capacity of 2 dm?3 at 37°C. Solid potato waste was packed into the digester and the organic content of the waste was released by microbial activity by circulating water over the bed, using batch loads of 500 g or 1000 g potato waste. The sequence of appearance of the volatile fatty acids was (acetic, propionic); (n‐butyric); (n‐valeric, iso‐valeric, caproic); (iso‐butyric). After 300 h digestion of potato waste on a small scale, the fermentation products were chiefly (mg g?1 total VFAs): acetic acid (420), butyric acid (310), propionic acid (140) and caproic acid (90), with insignificant amounts of iso‐butyric acid, n‐valeric and iso‐valeric acids. When the load of potato solids was increased, the volatile fatty acid content was similar, but butyric acid constituted 110 mg g?1 and lactic acid 400 mg g?1 of the total volatile fatty acids. The maximum soluble chemical oxygen demand (COD) achieved under the experimental conditions used was 27 and 37 g COD dm?3 at low and high loadings of potato solids, respectively. The total volatile fatty acids reached 19 g dm?3 of leachate at both loads of potato solid waste. Gas production was negligible, indicating that methanogenic activity was effectively inhibited. Copyright © 2004 Society of Chemical Industry 相似文献
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以水稻秸秆为原料,利用自行设计的渗滤床反应器,对比研究了不同温度(20、25、30和35℃)及不同预处理方式(NaOH、生物试剂和沼液)对秸秆厌氧发酵产气性能、物能转化率、发酵后沼液性能和产气成本等方面的影响。实验结果表明:发酵后总固体(TS)质量分数稳定在13%~15%之间,属于半固态厌氧发酵,同时累积产气量与温度、发酵后COD及NH3-N的变化量均呈极显著正相关。相同温度(20~30℃)条件下,经预处理后的水稻秸秆TS产气率较空白均有所提高;其中沼液预处理效果最为明显,35℃条件下,TS产气率及挥发性固体(VS)产甲烷率分别为154.0和55.2 mL/g,较空白样品分别提高25.1%和52.5%。同时,沼液预处理可显著提升厌氧发酵产气中的甲烷体积分数。各预处理样品TS产甲烷率及VS产甲烷率呈随温度(20~30℃)上升而增加的趋势,但产甲烷提升率随温度的上升而逐渐下降,将系统温度从20℃提升至25℃,各处理产甲烷率可提高90%以上。考虑到沼气工程罐体增温及产能收支平衡等因素,温度控制在25℃是经济性最好的策略模式。从产气成本上分析,自产沼液具有较佳的处理效果和较低的生产成本,每生产1 m3沼气的可变成本1.62元。 相似文献