生物过滤塔是一种典型的生物膜反应器，在处理挥发性有机物（VOCs）气体时，存在启动期性能低、对难降解VOCs去除能力弱和低温条件下运行性能差等问题。群感效应（QS）是QS信号分子激活基因表达的现象，对生物膜形成具有重要意义。基于QS对生物膜进行调控，有望改善VOCs生物过滤塔的运行性能。本研究构建了“直接添加QS信号分子”和“添加QS信号分子分泌菌”两种方法，探究了QS强化方法对生物过滤塔启动性能、难生物降解VOCs处理性能和低温运行性能的改善效果，并系统研究了QS强化方法对生物过滤塔生物膜的调控机制。选取酰化高丝氨酸内酯（AHLs）作为典型QS信号分子，通过单因素实验和响应面优化实验，优化了AHLs添加配方，优化后的配方为59 nmol·L-1 3O-C12-HSL、126 nmol·L-1 C11-HSL和 300 nmol·L-1 C12-HSL。筛选出一株具有较高AHLs分泌能力的细菌，鉴定为Acinetobacter菌。考察了添加外源AHLs对生物过滤塔处理甲苯气体的性能及生物膜的影响，结果表明外源AHLs能够提升生物过滤塔启动期的甲苯去除率，提高生物膜的生长量、胞外聚合物（EPS）含量和粘附强度。研究了两种QS强化方法对生物过滤塔处理氯苯气体性能及塔内生物膜的影响。结果表明，添加外源AHLs和AHLs分泌菌使氯苯平均去除速率从50 g·m-3·h-1分别提升至73 g·m-3·h-1和77 g·m-3·h-1，生物膜湿重分别从29 kg·m-3增至60 kg·m-3和39 kg·m-3，并且使生物膜的分布更加均匀、EPS含量和粘附强度更高。添加外源AHLs会降低生物膜中微生物群落的多样性，而添加AHLs分泌菌则会增加生物膜微生物群落的多样性。考察了两种QS强化方法对生物过滤塔低温运行性能和生物膜的影响。在塔内平均气温为12 °C时，添加外源AHLs和AHLs分泌菌分别使平均甲苯去除速率提高了39%和26%、平均矿化率提高了18%和25%、生物膜平均浓度提升了48%和87%，并且使生物膜的分布更加均匀、EPS含量和粘附强度更高。两种QS强化方法都促进了生物膜内孔道结构的构建、降低了生物膜极性以及增加了对甲苯的溶解能力，从而促进了VOCs的传质。综上所述，本研究构建了基于QS调控生物膜并改善VOCs生物过滤塔运行性能的方法，揭示了QS强化方法对生物过滤塔运行性能的改善效果和对生物膜的调控机制，为解决生物过滤技术的瓶颈问题提供了可行方案。
Biofilter is a typical biofilm reactor for volatile organic compounds (VOCs) gas treatment. The main challenges for biofilters treating VOCs are low performance in start-up phase, low removal capacity for refractory VOCs and poor performance at low temperature. Quorum sensing (QS) is a phenomenon of activating gene expression by QS signaling molecules, which is of great significance for biofilm formation. To enhance the biofilm formation in biofilters by QS regulation is expected to improve the biofilter performance and solve these problems. In this study, two QS enhancement methods, adding exogenous acyl-homoserine lactones (AHLs) and AHLs-producing bacteria were developed. The effects of QS enhancement on the performances of biofilters in startup phase, treating refractory VOCs and at low temperature were investigated. Morever, the mechanism of QS enhancement on biofilm in biofilter was systematically studied.AHLs were selected as the typical QS signaling molecules. The recipe of AHLs additavite was optimized by single-factor experiment and response surface optimization experiment, and the optimized recipe was 59 nmol·L-1 3O-C12-HSL, 126 nmol·L-1 C11-HSL and 300 nmol·L-1 C12-HSL. A strain with high AHLs producing capacity was screened, and was identified as Acinetobacter. The effects of the exogenous AHLs on biofilm and the performance of biofilter for gaseous toluene removal were investigated. The results showed that the addition of exogenous AHLs could enhance acclimazation toluene removal, biofilm growth, extracellular polymeric substance (EPS) production and the microbial adhesive strength of biofilm.The effects of two QS enhancement methods on the performance and biofilm of biofilters treating chlorobenzene were investigated. The average chlorobenzene elimination capacities of two biofilters, one with AHLs addition and the other with AHLs producing strain inoculation were 73 and 77 g·m-3·h-1 respectively, which were higher than that of control biofilter for 50 g·m-3·h-1. The wet biomass concentrations of two biofilters with QS enhancement were 60 and 39 kg·m-3 respectively, which were also higher than that of control for 29 kg·m-3. Analysis on biofilms showed that distribution uniformity, EPS production and adhesive strengths of biofilms were all prompted by the two QS enhancement methods. Adding exogenous AHLs decreased the diversity of microbial community in the biofilm, while AHLs-producing strain inoculation increased the diversity.Two QS enhancement methods were also applied in biofilters treating gaseous toluene at a low temperature of 12 °C, and their effects on biofilter performance and biofilm were stuied. The results showed that adding exogenous AHLs and AHL-producing bacterium in biofilters raised the average toluene elimination capacity by 39% and 26% respectively, and raised the average mineralization rate by 18% and 25% respectively, while compared with the control biofilter. In addition, the two QS enhancement methods could increase the biomass concentration by 48% and 87% respectively and made the biofilm distribute more uniform by increasing its EPS content and microbial adhesive strength. The two QS enhancement methods resulted in formation of more mesopores in biofilm, low polarity of biofilm, and increase in toluene solubility in biofilm, which all benefit VOCs mass transfer in biofilters.To sum up, this study successfully developed two biofilm regulation methods in biofilters based on QS enhancement. The improvement effects and their mechanism of these QS enhancement methods on biofilm formation and performance of biofilters treating VOCs were demonstrated. These results provide a strong support for solving the bottleneck problem of VOCs biofiltration technology.
