一株耐受低pH、高浓度硒菌株的筛选鉴定及两阶段pH调控高效除硒的研究

通过酸性含硒平板和摇瓶筛选出一株对低pH、高浓度硒有很好耐受性的菌株Y1,通过菌落形态特征分析和26S rDNA测序,鉴定该菌株为Pichia kudriavzevii,多抗性实验结果显示该菌是一株多重耐受性毕赤酵母。通过摇瓶实验研究了温度、接种量、摇床转速、pH对菌株除硒性能的影响,结果显示当温度为25℃,接种量为12%(v/v),摇床转速为250 r/min,pH为3.0时,菌株对硒的去除率最高为58.3%。基于不同pH发酵过程中菌体生物量及富硒量的不同表现:pH 3.0时生物量最高,pH 5.0时富硒量最高,提出两阶段pH调控策略:发酵0 h~14 h将pH控制在3.0,14 h~28 h将pH控制在5.0,最终除硒率可达78.6%,分别比pH恒定在3.0及5.0条件下提高了15.4%和21.7%。

Isolation and identification of a low-pH and selenium tolerant strain and research on efficient removal of selenium using two-stage pH control strategy

The strain Y1 with low pH and high concentration of selenium tolerant was screened by acidic selenium-containing plate and shake flask.This strain was identified as Pichia kudriavzevii by 26S rDNA sequence and morphology characteristics.Multi-stress test results showed that the strain could be described as a multi-stress-tolerant yeast.The effects of temperature,inoculation amount,shaking speed and pH on the selenium removal performance of the strain was studied by shake flask experiment.The results showed that the maximum removal rate of selenium was under the following conditions:temperature 25 ℃,inoculation amount 12％ (v/v),shaking speed 250 r/min and pH 3.0.Based on specific biomass and specific Se bioaccumulation under different pH conditions:there was the maximum biomass at pH 3.0 and the maximum Se bioaccumulation at pH 5.0.A two-stage pH control strategy was therefore developed,i.e.pH was controlled at 3.0 in the first stage of fermentation (0 h ～14 h) and then switched to pH 5.0 in the second stage (14 h ～28 h).The final removal rate could reach to 78.6％.It was 15.4％ higher than that of pH 3.0 and 21.7％ higher than that of pH 5.0,respectively.