The relative effectiveness of pH control and heat treatment for enhancing biohydrogen gas production
The relative effectiveness of pH control and heat treatment for enhancing biohydrogen gas production
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DOI：
10.1021/es034291y
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发表时间：
2003-11-15
影响因子：
11.4
通讯作者：
Logan, BE
中科院分区：
文献类型：
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作者：
Oh, SE;Van Ginkel, S;Logan, BE
当阻止种间氢转移到产甲烷菌时，可以从有机基质的高浓度微生物发酵中回收氢气。已用于限制混合培养物中的产甲烷的两种技术是热处理，以从接种物中去除非产孢产甲烷菌，以及培养物生长期间的低pH。我们发现在所有试验中产生高氢气浓度（57-72%），并且接种物的热处理（HT）（pH 6.2或7.5）产生比低pH（6.2）条件下未热处理的接种物（NHT）更大的氢气产率。葡萄糖向氢气的转化效率（基于4 mol-H-2/mol-glucose的理论产率）如下：24.2%（HT，pH = 6.2）、18.5%（HT，pH = 7.5）、14.9%（NHT，pH = 6.2）和12.1%（NHT，pH = 7.5）。在分批试验中，葡萄糖（3g-COD/L）利用（大于或等于99%）的主要产物是乙酸（3.4-24.1%）、丁酸（6.4-29.4%）、丙酸（0.3-12.8%）、乙醇（15.4-28.8%）和氢气（4.0-8.1%），以及少量的丙酮、丙醇和丁醇（以COD计）。所有分批培养物中的氢气相浓度在30小时后达到最大值57-72%，但此后在80小时内迅速下降至不可检测的水平。单独的实验表明，大量的氢损失可能会发生通过产乙酸和热处理不能防止产乙酸。热处理始终消除了可测量浓度的甲烷的产生。在氢气生产过程中产生的乙醇的消失可能是由于乙酸的产生，因为热力学计算表明，一旦氢气耗尽，该反应是自发的。总之，这些结果表明，在没有热处理的情况下，低PH足以控制混合分批培养物中产甲烷菌的氢损失，并表明需要找到限制产乙酸的方法，以增加分批培养物的氢气产率。
Hydrogen gas can be recovered from the microbial fermentation of organic substrates at high concentrations when interspecies hydrogen transfer to methanogens is prevented. Two techniques that have been used to limit methanogenesis in mixed cultures are heat treatment, to remove nonsporeforming methanogens from an inoculum, and low pH during culture growth. We found that high hydrogen gas concentrations (57-72%) were produced in all tests and that heat treatment (HT) of the inoculum (pH 6.2 or 7.5) produced greater hydrogen yields than low pH (6.2) conditions with a nonheat-treated inoculum (NHT). Conversion efficiencies of glucose to hydrogen (based on a theoretical yield of 4 mol-H-2/mol-glucose) were as follows: 24.2% (HT, pH = 6.2), 18.5% (HT, PH = 7.5), 14.9% (NHT, pH = 6.2), and 12.1% (NHT, pH = 7.5). The main products of glucose (3 g-COD/L) utilization (greater than or equal to99%) in batch tests were acetate (3.4-24.1%), butyrate (6.4-29.4%), propionate (0.3-12.8%), ethanol (15.4-28.8%), and hydrogen (4.0-8.1%), with lesser amounts of acetone, propanol, and butanol (COD basis). Hydrogen gas phase concentrations in all batch cultures reached a maximum of 57-72% after 30 h but thereafter rapidly declined to nondetectable levels within 80 h. Separate experiments showed substantial hydrogen losses could occur via acetogenesis and that heat treatment did not prevent acetogenesis. Heat treatment consistently eliminated the production of measurable concentrations of methane. The disappearance of ethanol produced during hydrogen production was likely due to acetic acid production as thermodynamic calculations show that this reaction is spontaneous once hydrogen is depleted. Overall, these results show that low PH was, without heat treatment, sufficient to control hydrogen losses to methanogens in mixed batch cultures and suggest that methods will need to be found to limit acetogenesis in order to increase hydrogen gas yields by batch cultures.