餐厨垃圾厌氧发酵产酸优化及蛋白质组分的产酸特性研究

发布时间：2018-05-27 17:20

本文选题：挥发性脂肪酸 + 餐厨垃圾　；参考：《浙江工商大学》2017年硕士论文

【摘要】：挥发性脂肪酸(VFAs),作为合成许多生物能源(氢气和甲烷等)的前体,在工业上有广泛的应用。目前,VFAs的合成主要通过化学方法,但该法耗能巨大;而利用生物法(厌氧发酵技术)合成VFAs具有一定的优越性。厌氧发酵是一种基于生物质生成高附加值产物的可再生过程。餐厨垃圾中有机物含量较高,适宜通过厌氧发酵技术生产VFAs。利用餐厨垃圾厌氧发酵生产挥发性有机酸的研究也逐渐兴起,但该过程仍存在较多的限制性因素。基于餐厨垃圾厌氧发酵产酸过程中存在的预处理方法的非经济性、厌氧条件的难控制性以及垃圾组分的低转化率等问题展开本文的研究。首先,评估了一种经济环保的预发酵处理方式对餐厨垃圾产酸的作用;并将其与水热预处理联合,观察它们对产酸效果的影响,初步探究产酸机理。其次,探究氧化还原电位(ORP)对餐厨垃圾水解产酸的影响规律,结合微生物群落结构分析产酸机理,明确最佳的发酵产酸条件。最后,研究餐厨垃圾中不同蛋白质组分发酵产酸的特性,分析剩余蛋白的组成,明确其转化效率低的限制性因素。本文主要获得以下结论:(1)预发酵和预发酵+水热预处理可以有效地促进有机物的溶出和水解。餐厨垃圾预发酵处理形成的低pH环境有利于多聚糖的糖化,从而促进碳水化合物的水解。预发酵+水热处理则更有利于一些复杂基质(纤维素和蛋白质等)的溶出。预处理后的餐厨垃圾在厌氧发酵初期产酸速率明显增加。但是由于餐厨垃圾本身的高纤维素和高油脂含量,后期总产酸量受到抑制。此外,不同预处理的餐厨垃圾发酵产酸的途径存在差异:预发酵处理的餐厨垃圾先转化为乳酸,而后乳酸再转化为VFAs;,预发酵+水热处理后的垃圾则直接转化为VFAs。经济性评估表明,预发酵+水热处理是一种高产酸、低能耗的预处理方法(尤其对低油脂和低纤维素含量的餐厨垃圾而言)。(2)在pH6的产酸体系中,厌氧环境(ORP-200～-300 mV)并不利于产酸,而最适合餐厨垃圾发酵产酸的ORP范围是-100～-200 mV。在保持最佳ORP水平时,接种厌氧微生物有利于促进有机质(尤其是蛋白质)的降解;且该体系中微生物多样性更丰富,Firmicutes的相对丰度更大,产酸量(0.79g COD/g VS)更多。厌氧发酵反应器中2-溴乙烷磺酸盐(BES)的添加可以提高产酸量,主要是因为其增加了反应体系中产酸菌的丰度。(3)相同有机物含量的鸡蛋蛋白和豆腐的发酵产酸量和产酸组成明显不同。水热预处理对于鸡蛋蛋白的生物转化是不利的。豆腐产酸以乙酸为主(乙酸型发酵);而鸡蛋蛋白所产的各种有机酸的比例相近(混合酸型发酵)。两种蛋白质的产酸途径也有差异:豆腐产酸严格地按照Stickland反应进行,蛋白质水解为氨基酸,氨基酸直接转化为乙酸、丙酸、丁酸和戊酸;鸡蛋蛋白产酸除了转化为乙酸、丙酸、丁酸和戊酸之外,同时合成大量乳酸。不同反应器中产酸量的差异也归因于其中微生物群落结构的差异。Sporanaerobacter和Aminobacterium分别是豆腐(21.0%)和鸡蛋蛋白(10.9～19.9%)产酸体系中的优势微生物;而且在鸡蛋蛋白产酸反应器中检测到更多的乳酸菌(Leuconostoc,Lactobacillus)根据氮平衡分析可知,所有反应器中蛋白质的转化效率与其产酸效率具有一致性。发酵结束时,所有反应器中仍剩余部分可溶性蛋白(占总蛋白的30～40%)未降解。通过蛋白质分离,结果表明水热处理后的两种蛋白产酸体系中,剩余可溶性蛋白中约50%以蛋白酶的形式存在。
[Abstract]:Volatile fatty acids (VFAs) are widely used in industry as precursors for the synthesis of many bioenergy sources (hydrogen and methane). At present, the synthesis of VFAs is mainly through chemical methods, but this method has great energy consumption, and the synthesis of VFAs by biological method (anaerobic fermentation technology) has some advantages. Anaerobic fermentation is a kind of biomass based production. The regenerative process of high added value products. The content of organic matter in food waste is high. The research on the production of volatile organic acids by anaerobic fermentation by anaerobic fermentation technology by anaerobic fermentation technology is also gradually rising, but there are still many restrictive factors in this process. Based on the pretreatment of anaerobic fermentation of kitchen waste in the process of acid production, VFAs. The non economy of treatment, the difficult control of anaerobic conditions and the low conversion rate of the garbage components are studied in this paper. First, the effect of a kind of economic and environmental pre fermentation on the acid production of kitchen waste is evaluated, and the effect of them on the effect of acid production is observed and the effect of them on the acid producing effect is observed and the acid production is preliminarily explored. Secondly, the effect of the oxidation reduction potential (ORP) on the hydrolytic acid production of kitchen waste was investigated, and the optimum fermentation acid producing condition was determined by analyzing the mechanism of acid production by microbial community structure. Finally, the characteristics of acid production by different protein components in food waste were studied, the composition of the residual protein was analyzed, and the limitation of the conversion efficiency was clear. The main conclusions are as follows: (1) pre fermentation and pre fermentation + hydrothermal pretreatment can effectively promote the dissolution and hydrolysis of organic compounds. The low pH environment formed by pre fermentation of kitchen waste is beneficial to the saccharification of polysaccharides, thus promoting the hydrolysis of carbohydrates. Dissolution of cellulose and protein. The rate of acid production of kitchen waste in the early stage of anaerobic fermentation increased significantly. However, the total acid content in the later period was inhibited because of the high cellulose and high oil content of the kitchen waste itself. In addition, the ways of producing acid by different pretreated kitchen waste fermentation were different: the pretreated kitchen kitchen waste The garbage was converted to lactic acid first and then the lactic acid was converted to VFAs, and the pre fermentation and hydrothermal treatment was directly converted to the VFAs. economic assessment. The prefermentation and hydrothermal treatment was a high-yield acid, low energy consumption pretreatment method (especially for low oil and low cellulose content). (2) in the acid producing system of pH6, anaerobic digestion was anaerobic. The environment (ORP-200 to -300 mV) is not favorable for acid production, and the ORP range that is most suitable for food waste fermentation is that -100 to -200 mV. can promote the degradation of organic matter (especially protein) when maintaining the optimum ORP level, and the microbial diversity is more abundant, the relative abundance of Firmicutes is greater, and the acid yield is 0. .79g COD/g VS) more. The addition of 2- bromine ethane sulfonate (BES) in anaerobic fermentation reactor can increase acid production, mainly because it increases the abundance of acid bacteria in the reaction system. (3) the acid content and acid composition of the egg protein of the same organic content and the fermented bean curd are distinctly different. The conversion is unfavorable. The acid of bean curd is mainly acetic acid (acetic acid fermentation); and the proportion of all kinds of organic acids produced by egg protein is similar (mixed acid fermentation). The acid producing ways of the two kinds of proteins are also different: the bean curd produces acid strictly according to the Stickland reaction, the protein is hydrolyzed to amino acid, the amino acid is directly converted into acetic acid, propionic acid, Butyric acid and valerate; egg protein acids are produced in addition to acetic acid, propionic acid, butyric acid and valerate, and a large amount of lactic acid is synthesized. The difference in acidity in the different reactors is also attributed to the differences in microbial community structure between.Sporanaerobacter and Aminobacterium in the acid producing system of tofu (21%) and egg protein (10.9 to 19.9%), respectively. Dominant microorganisms, and more lactic acid bacteria (Leuconostoc, Lactobacillus) detected in egg protein acid producing reactor (Leuconostoc, Lactobacillus), according to nitrogen balance analysis, the conversion efficiency of protein in all reactors is consistent with the efficiency of acid production. At the end of the fermentation, all the remaining soluble proteins in all reactors (30~4 of the total protein) 0%) undegraded. Through protein separation, the results showed that about 50% of the remaining soluble proteins were found in the form of protease in the two protein producing systems after hydrothermal treatment.
【学位授予单位】：浙江工商大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ921;X799

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