Sustainable bioproducts from low cost methane gas

Lead Research Organisation: University of Nottingham
Department Name: School of Life Sciences


BACKGROUND: To compete with existing biopruducts manufacturing processes based on petrochemical derived raw materials, low cost feedstocks for biological fermentation processes are essential, since the feedstock typically equates to >60% of the overall production cost. In addition, the yield based on carbon needs to be high, which is very difficult to achieve with sugars or cellulosic feedstocks with a high oxygen content, since the oxygen is lost as CO2. Methane (CH4) is an abundant and cheap carbon resource, but is currently under-utilised as a feedstock for industrial biotechnology. Surplus methane is often released during oil extraction and simply flared (burnt without capturing the energy or carbon content). Many natural gas reserves are 'stranded' and uneconomic to recover. Methane is also a major component of biogas produced on a large scale by anaerobic digestion, technology that is well established in the EU. Currently, most biogenic methane is burnt for energy and has relatively little value. Today, methane is a low cost fermentation feedstock and also sustainable given the many sources available and current wastage. Therefore, methane provides an exciting feedstock opportunity for fermentation and conversion into high value biochemical metabolites (lipids, proteins and feeds). As the world leading methane-based protein producer, Calysta has filed patents for the use of methanotrophs in the commercial-scale production of nutritional ingredients, chemicals, biofuels and feed from methane. A disruptive production process based on CH4 would accelerate the growth and market penetration of biobased products considerably.
Aerobic methanotrophs represent the only available route for methane bioconversion, activating methane to methanol via methane monooxygenase (MMO) and subsequently converting methanol to formaldehyde en route to by-products. There are currently more than 15 recognised genera of methanotrophs, with many recent publications showing the isolation of new species or strains and genome sequences, within which Methylococcus capsulatus is the model organism and the most common chassis in attempts to produce biomass for use as single-cell protein in animal feed.
As part of BBSRC NIBB C1Net POC (Metabolic modelling to support synthetic biology in C1Net organisms) project, a genome scale model (GSM) of M. capsulatus (Bath) was generated on the basis of the annotation obtained from BioCyc. This model was shown to represent a cell system capable of generating all amino acids, nucleotides, generic lipid and carbohydrate using methane as the sole carbon source. It was also shown that the cell is capable of generating the industrially useful bioproducts such as succinate. This GSM will be used in the project.

AIM: In this project, we will explore the bottlenecks of using methane as a feedstock in continuous fermentations in both lab (1L, 10L) and demo (5000L) scales; to improve the rates and energy efficiencies of methane uptake, as well as approaches to engineer high-productivity methane conversion organisms.

STRATEGY: Our aim will be progress through the following activities:- (i) identifying M.capsulatus growth bottlenecks in fermenters through meticulous designed RNA seq experiments; (ii) implementing the requisite random mutagenesis transposon technologies in M. capsulatus; (iii) using semi-robotic high throughput technology screening for desired phenotype and thereafter the gene/genes affecting; (v) follow GSM's instruction, rational knock out genes and pathways to increase CH4 assimilation.

Working with one of the world's leading C1 companies, the student will develop and demonstrate the potential of M. capsulatus as whole cell protein feed from low cost methane gas. This will allow avoidance of competition with food and land resources while at the same time providing benefits to the environment and society through a reduction in GHG emissions.


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