Design of a bacterial consortium for consolidated bioprocessing

PI: Schmidt-Dannert, Claudia

Proposal Number: 1235714

Institution: University of Minnesota-Twin Cities

Title: Design of a bacterial consortium for consolidated bioprocessing

Biotechnological bioprocesses typically use pure cultures of metabolically engineered microbial strains. In contrast, environmental processes generally utilize the metabolic diversity present in native microbial consortia to accomplish tasks that not one single organism can do alone. The quest for the development of consolidated bioprocesses for biofuel production, where hydrolysis of recalcitrant lignocellulosic biomass and subsequent sugar conversion into biofuels are combined, has reinvigorated investigations into the use of mixed cultures. Currently different strategies are being pursued to obtain strains that are both lignocellulolytic and advanced biofuel producers, but so far none of the engineered strains is efficient at both tasks.

The engineering of biological networks with new emergent properties employed in the field of synthetic biology has provided tools and strategies with which it becomes possible to design and investigate synthetic microbial consortia. By compartmentalizing metabolic functions into separate microbial populations, the metabolic network of each strain can be optimized for distinct tasks that together result in the production of a desired compound. The different engineered microbial strains co-cultured in a bioprocess can therefore be considered as individual metabolic modules that may be exchanged or augmented with additional modules. Prerequisite for the engineering of such mixed microbial communities, however, is the establishment of population control systems.

This project will design a prototype synthetic microbial community as a proof-of-concept for consolidated bioprocessing. Results from the proposed research can guide the development of other bioprocesses using engineered microbial consortia. Specifically, this project will engineer a mixed culture consisting of B. subtilis, Rhodococcus opacus and E. coli for de novo biodiesel production. The industrial protein expression host B. subtilis will be engineered to secrete cellulolytic enzymes for sugar release from biomass, while the oleaginous R. opacus and the ethanologenic E. coli strain together will convert sugars into fatty acid ethyl esters (biodiesel). Key to the development of such a consortium is the engineering and configuration of adequate systems to control growth of each consortium member in accordance to the requirements of the process. The project will design such population control systems using components of bacterial quorum sensing systems. A system simulation model will be built to guide us in the design these control systems.

The project will provide a proof-of-concept for the development and application of engineered microbial consortia for bioprocessing. The use of mixed cultures for biotechnology may thus be revitalized and moved from the pre-DNA technology into the synthetic biology area. Results from this application will provide insights and a model for the design of population control systems needed to adjust population sizes to the requirements of a specific process. The proposed research will impact the field of biotechnology and synthetic biology. Findings of this research may lead to new and more efficient approaches for biofuel production and other bioproduction processes. The proposed research will provide training in genetic and metabolic engineering for one postdoctoral researcher and four undergraduate students.