College of Environmental Science and Engineering, Hunan University, Changsha 410082, People's Republic of China.
Appl Microbiol Biotechnol. 2013 Jun;97(12):5597-604. doi: 10.1007/s00253-012-4378-4. Epub 2012 Sep 6.
In this investigation, the effect of pH (4.0-11.0) on waste-activated sludge (WAS) hydrolysis and acidification in the presence of a biosurfactant rhamnolipid (RL) were studied. The results showed that the hydrolysis and acidification of WAS in the presence of RL at alkaline pH values were more efficient than that at acidic and near-neutral pH values. After 6 h of hydrolysis, the soluble protein and carbohydrate were 1,654.7 and 675.9 mg/L (pH 11.0), and 825.6 and 376.0 mg/L (pH 7.0), whereas the values were only 315.0 and 84.0 mg/L at pH 4.0 and 164.1 and 32.0 mg/L for the blank, respectively. After 2 or 3 days of fermentation, the accumulated short-chain fatty acids (SCFAs) reached the highest and then decreased with a further increase in time at all investigated pH values. The analysis of SCFA compositions showed that acetic, propionic, and iso-valeric acids were the three main products at any pH value. A higher pH contributed to a greater proportion of acetic acid and a lesser proportion of iso-valeric acid; a lower pH resulted in a greater proportion of iso-valeric and lesser proportion of acetic acid in the initial fermentation. The proportions of acetic acid for the system with biosurfactant RL addition were 16.65, 36.33, and 62.94 %, respectively, at pH 4.0, 7.0, and 11.0 after 1 day. Correspondingly, the proportions were 40.34, 12.60, and 11.01 % for iso-valeric acid.
在这项研究中，考察了生物表面活性剂鼠李糖脂（RL）存在下 pH（4.0-11.0）对剩余活性污泥（WAS）水解酸化的影响。结果表明，碱性 pH 值下 RL 存在时 WAS 的水解酸化比酸性和近中性 pH 值下更有效。经过 6 h 的水解，在 pH 值为 11.0 时，可溶性蛋白质和碳水化合物分别为 1654.7 和 675.9 mg/L，在 pH 值为 7.0 时，分别为 825.6 和 376.0 mg/L，而在 pH 值为 4.0 时，仅为 315.0 和 84.0 mg/L，空白组分别为 164.1 和 32.0 mg/L。经过 2 或 3 天的发酵，在所有考察的 pH 值下，短链脂肪酸（SCFA）的积累达到最高，然后随着时间的延长而减少。SCFA 组成分析表明，在任何 pH 值下，乙酸、丙酸和异戊酸都是三种主要产物。较高的 pH 值有利于乙酸比例增加和异戊酸比例减少；较低的 pH 值导致初始发酵中异戊酸比例增加和乙酸比例减少。在添加生物表面活性剂 RL 的系统中，pH 值分别为 4.0、7.0 和 11.0 时，经过 1 天，乙酸的比例分别为 16.65%、36.33%和 62.94%，而异戊酸的比例分别为 40.34%、12.60%和 11.01%。
