通过响应面法确定产气克雷伯氏杆菌(Klebsiella aerogenes)产胞外聚合物(EPS)的最优培养条件,并开展EPS质量浓度对Klebsiella aerogenes诱导形成碳酸钙晶型影响的试验研究.研究结果表明,相较于pH和接种量,培养时间和温度对菌株EPS产量的影响更为显著,EPS最优培养条件如下:培养时间为4.64 d、培养温度为28.35℃、接种量为2.97%、pH=7.69,在此条件下,EPS的产量可达210.24 mg/L;当添加的EPS质量浓度从0 g/L增加到1.0 g/L时,方解石的质量分数从27.1%提高至98.3%,球霰石的质量分数从72.9%下降至1.7%,表明EPS能有效促进方解石的形成并抑制球霰石的形成;EPS中带负电荷的官能团可以吸附溶液中Ca2+,使得溶液中Ca2+浓度减小、过饱和度降低从而促进方解石型碳酸钙晶体的生成.可以通过EPS来调控Klebsiella aerogenes诱导形成方解石和球霰石的质量分数,强化碳酸钙晶体向热力学稳定的方解石型碳酸钙转化,这为提高微生物诱导碳酸钙沉淀形成的固化体的力学强度提供了新的思路.
The optimal culture conditions of extracellular polymeric substances(EPS)produced by Klebsiella aerogenes were determined by response surface,and the experiments were conducted to investigate the effect of EPS on the formation of calcium carbonate crystals induced by Klebsiella aerogenes.The results show that the effects of cultivation time and temperature on EPS production are more significant than those of pH and inoculation amount by Klebsiella aerogenes.The optimal cultivation conditions for EPS production are the cultivation time of 4.64 d,cultivation temperature of 28.35℃,inoculation amount of 2.97%,and cultivation pH of 7.69.Under the optimal cultivation condition,the EPS production reaches 210.24 mg/L.The percentage of calcite increase from 27.1%to 98.3%and the percentage of vaterite decreased from 72.9%to 1.7%,when the additional EPS mass concentration is increased from 0 g/L to 1.0 g/L.EPS can effectively promote the formation of calcite and inhibit the formation of vaterite.The negatively charged functional groups in EPS can adsorb Ca2+ from the solution,resulting in the reduction of Ca2+ concentration and CaCO3 supersaturation in the solution,which promotes the formation of calcite.The ratio of calcite and vaterite induced by Klebsiella aerogenes can be regulated by additional EPS.The conversion of calcium carbonate crystal to calcite with thermodynamic stability is enhanced by the EPS of Klebsiella aerogene,which provides a new way for improving the mechanical strength of solidified samples induced by microbial induced calcium carbonate precipitation.