果蔬废弃物两相厌氧发酵产己酸的效能研究

Two-phase Caproate Fermentation from Fruit and Vegetable Waste

利用厌氧菌群生物合成己酸被认为是一种非常有潜力的新型废弃物资源化技术,但是其合成效能的提高是目前亟待解决的关键问题。本研究以实际果蔬废弃物为原料,对两相厌氧发酵产己酸的效能进行了研究。首先优化接种比以提高酸化相的水解转化效率;在此基础上通过调控醇酸比和pH以强化产己酸相的发酵效能。结果显示,果蔬废弃物厌氧产酸的最佳接种比为2∶1,此时水解率和酸化率分别可达到98.1%和83.2%,乙酸和丁酸产量分别达到5.4 g/L和3.3 g/L。合理控制醇酸比和pH对提高产己酸相的发酵效能非常关键。当醇酸比和pH控制为4∶1和7.5时,己酸生成量可达14.9 g/L,约占液相总COD的80.84%;而低醇酸比和低pH易造成丁酸的累积,从而降低了己酸产量。己酸发酵过程属于非生长偶联型,己酸菌(Clostridium kluyveri)指数增长期伴随着丁酸的生成,而己酸合成主要发生在生长中后期。此外,己酸菌对于pH变化较为敏感,适当提高pH有助于减轻有机酸毒性,提高生物量;但是碱性环境会严重抑制己酸菌的生长繁殖。研究表明,通过分别对酸化相和产己酸相进行优化和调控,两相发酵策略更有利于提高己酸合成效能。

Caproate fermentation from organic waste via anaerobic mixed culture is considered as a promising new technology for energy and resource recovery.However,relatively low productivity limits its application.In this paper,the performance of two-phase anaerobic caproate fermentation using actual fruit and vegetable waste was studied.Inoculation to substrate ratio influenced the hydrolysis efficiency in acidified phase,based on the optimized ratio,influences of ethanol to acid ratio and p H on the fermentation efficiency of the production of caproate fermentation phase were studied.The results showed that the optimal ratio of anaerobic acid production of fruit and vegetable waste was 2 ∶1.The hydrolysis rate and acidification rate were 98.1% and 83.2%,respectively.The acetate and butyrate production reached 5.4 g/L and 3.3 g/L respectively.Rational control of the ratio of ethanol/acid and pH is critical to improve the fermentation efficiency of the caproate-producing phase.When the ratio of ethanol to acid ratio and p H was 4 ∶1 and 7.5,caproate production reached 14.9 g/L,which accounted for about 80.84% of the liquid total COD.However,low ethanol to acid ratio and low pH caused the accumulation of butyrate,thereby reducing the production of caproate.The caproate fermentation process is non-growth-coupled,and the growth period of the Clostridium kluyveri exponent is accompanied by the production of butyrate,and the synthesis of caproate occurs mainly in the later growth stage.In addition,caproate-producing bacteria was sensitive to changes in pH.Properly increasing the pH will help reduce the toxicity of organic acids and increase biomass.However,the alkaline environment will severely inhibit the growth and reproduction of caproate bacteria.Studies had shown that the two-phase fermentation strategy was more conducive to improve caproate production by optimizing the acidification phase and the caproate-production phase,respectively.