Genetic engineering is a technology that has the potential to produce more useful microorganisms for bio-industry. One of the targets of our research is molecular breeding of microorganisms that are able to degrade complex plant cell wall fibers and produce biofuels. Degradation of plant cell wall requires many cellulolytic enzymes. Therefore, engineering of metabolic pathway and transcriptional mechanism is required for breeding microorganisms that can convert biomass to bioenergy efficiently. We are focusing on molecular genetics of anaerobic bacteria and filamentous fungi.