Harnessing unexplored mixed-cultured microbial communities towards development of a cost-effective and low-environmental burden bioprocess

Microorganisms in natural environments are known to be versatile. However, their functions and interactions among different microorganisms have not been unveiled. These unexplored microorganisms have important functions potentials and, therefore, need to be exploited to an engineered system. By integrating mathematical, microbiological and chemical engineering methods, we are tackling on the following missions (Figure 1): (1) attainment of these unexplored microorganisms, to intertwine complicated interactions among microorganisms; and (2) development of a bioprocess allowing to maximize functions. Based on the integrated approach, we are currently developing a cost-effective and energy-efficient biological wastewater treatment system and a bioprocess both to treat wastewater and to convert agricultural wastes into methane gas for energy recovery.

1. Development of a cost-effective wastewater treatment process using aerobic microorganisms and mitigation of greenhouse gases
We are currently developing an aerobic bioreactor system with high cost-effectiveness for nitrogen removal from wastewater. Nitrogen discharge into water bodies leads to eutrophication, which needs to be treated. By managing and controlling microorganism, we are capable of reducing operational cost of nitrogen removal. Via biological nitrogen removal, nitrous oxide (N2O), directly causing global warming and ozone depletion, is produced. We are trying to elucidate mechanisms to produce N2O during nitrogen removal, to acquire microorganisms responsible for N2O reduction and to develop a bioprocess harnessing these microorganisms.

2. Development of a "co-benefit" system achieving both wastewater treatment and biogas recovery
By mixing livestock wastewater, containing high concentration of nitrogen, with stalls of rice plant and lotus, we are also developing a co-benefit system achieving nitrogen removal from livestock wastewater and biogas recovery from the agricultural wastes (Figure 2). Water content derived from livestock wastewater is absorbed by the agricultural wastes; hence, the nitrogen contents are taken by the wastes, which can be fed as a highly-nutritious fertilizer. We are concomitantly investigating a way to control microbial consortium in a dry-thermophilic anaerobic digestion tank (Figure 2) to attain stable biogas production.