Isolation,Mutation Breeding And Application Of Electrochemically Active Bacteria

Electricigens,also known as extracellular respiratory bacteria（ERB）,or electrochemically active bacteria（EAB）,are a class of microorganisms capable of transferring electrons derived from their metabolism process to extracellular environment for anaerobic respiration.This unique extracellular electron transfer（EET）capability enables them to use anode as the electron acceptor in anaerobic respiration.The most extensively described device to utilize this EET process is microbial fuel cell（MFC）,in which the electricigens serve as the catalyst in anode to convert organic molecules into electricity.Despite the recent achievements on MFC research,the low catalytic efficiency of the electricigens in the anode is still one of the most important challenges for electricity production.Recently,the isolation and application of electricigens have received substantial attentions.More electricigens have been identified from bioreactors and natural environments through different ways.However,the multidiversity of electricigens suggests that there are still a lot of electricigens to be discovered.Our studies here focus on the isolation of new electricigens,the enhancement of power generation capacity of electricigens,and their application potiential for chemical transformations.Main contents and conclusions in this thesis are as follows:1.By using a rapid high-throughput method in a 96-well plate in which WO₃ nanomaterials served as a probe,we isolated a large number of electricigens from the river sediments.Two strains,designated as Lysinibacillus fusiformis A-5 and Lysinibacillus sphaericus D-8,were identified as electricigens for the first time.Their abilities to generate electricity were tested in two-chamber MFCs.Both cyclic voltammetry（CV）and electrochemical impedance spectroscopy（EIS）analysis confirmed the electrochemical acitivty of strain D-8.2.A novel atmospheric and room temperature plasma（ARTP）was used to generate mutants of Shewanella oneidensis MR-1 for improved electricity production.By using the high-throughput screening method that employs WO₃ nanoprobs in a 96-well plate,we obtained 10 mutants with stable enhanced relative color density（mean）compared to Shewanella oneidensis MR-1（wild type）after ten successive cultural generations.Two strains with better coloration were selected to characterize their electricity-generating capacity in MFC.The highest current densities produced by mutant Strain 1 and 5 were enhanced ca.38%and 12%,respectively,compared to the wild strain.Meanwhile,three mutant strains showed little ability in WO₃ coloration,and they could not generate current in MFCs.These results show that ARTP can be used as an effective tool to obtain mutants with high current generation capability.3.The potential to ustilize the isolated bacterial cultures L.fusiformis A-5 and L.sphaericus D-8 for biotransformation of methyl orange and nitrobenzene through non-specific electron transfer was studiesd.The results demonstrate that methyl orange A-5 could be partially degraded by A-5,while L.sphaericus D-8 could reduce nitrobenzene with N-acetyl-D-glucosamine and glycerol as the sole carbon source respectively.4.To make effective use of the phosphate solubilization capacity of Lysinibacillus fusiforrrmis A-5 and Lysinibacillus sphaericus D-8,we explored the role of these two strains in promoting the release of phosphorus from biochar.The results show that the content of soluble phosphate increased remarkably in the co-culture of the bacterial strains with biochar.This study provides an application potential for electricigens in phosphate solubilization.