Primary Investigator:  Judy Yang
Co-Investigators: William Wei (Postdoctoral Research Scholar)
Industry Partners: Ecolab
Award Type: Seed Grant – Graduate Research Scholar with NRRI Travel Grant

Problem: Each year, tens of millions of tons of lignin waste are produced worldwide in pulp and paper industries. The presence of lignin in wastewater is a serious environmental problem because lignin has low biodegradability and dark color. Recent studies suggest that bacterium Pseudomonas putida, a “workhorse” for bioremediation, can be used in moving bed biofilm reactors to biodegrade lignin in wastewater and convert it to bioproducts. The performance of the biofilm reactors is controlled by biofilm thickness and density; however, the optimum thickness and density of P. putida biofilms to degrade contaminants remain to be characterized and methods to control biofilm thickness and density are lacking.

Solution: Our goal is to develop a hydrodynamics-based method to optimize the biodegradation of lignin by controlling the thickness and density of P. putida biofilms. We plan to conduct systematically controlled experiments in a customized microfluidic platform to determine (1) the optimum thickness and density of P. putida biofilms that degrade lignin most effectively and (2) the hydrodynamic conditions to control biofilm thickness and density. We will quantify the thickness and density of biofilms and the concentration of naturally fluorescent lignosulfonates using a confocal laser scanning microscope, which has resolution as high as several tens of nanometers. We will conduct biofilm culture and lignin degradation experiments in systematically controlled hydrodynamic conditions, including controlled mean flow velocity and velocity fluctuations, to determine the optimum hydrodynamic condition to culture biofilms that can degrade lignin most effectively. 

Impact: Our study will provide a systematic method to control the degradation efficiency of lignin and other contaminants by biofilms. This method can be used in paper and pulp industries and wastewater plants to remediate lignin and other contaminants effectively. The microfluidics plus confocal imaging platform developed in this study can also be used to test the effectiveness of other biofilm control technologies, such as biofilm targeted chemical additives. Furthermore, the developed microfluidics plus confocal imaging method can be used to study the bioremediation effectiveness of other organisms, such as fungi. 

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