Title: Combined Effects of Carbon and Nitrogen Source to Optimize Growth of Proteobacterial Methanotrophs

Abstract

Methane, a potent greenhouse gas, and methanol, commonly called wood alcohol, are common by-products of modern industrial processes. They can, however, be consumed as a feedstock by bacteria known as methanotrophs, which can serve as useful vectors for biotransformation and bioproduction. Successful implementation in industrial settings relies upon efficient growth and bioconversion, and the optimization of culturing conditions for these bacteria remains an ongoing effort, complicated by the wide variety of characteristics present in the methanotroph culture collection. Here, we demonstrate the variable growth outcomes of five diverse methanotrophic strains - Methylocystis sp. Rockwell, Methylocystis sp. WRRC1, Methylosinus trichosporium OB3b, Methylomicrobium album BG8, and Methylomonas denitrificans FJG1 - grown on either methane or methanol, at three different concentrations, with either ammonium or nitrate provided as nitrogen source. Maximum optical density (OD), growth rate, and biomass yield were assessed for each condition. Further metabolite and fatty acid methyl ester (FAME) analyses were completed for Methylocystis sp. Rockwell and M. album BG8. The results indicate differential response to these growth conditions, with a general preference for ammonium-based growth over nitrate, except for M. denitrificans FJG1. Methane is also preferred by most strains, with methanol resulting in unreliable or inhibited growth in allmore » but M. album BG8. Metabolite analysis points to monitoring of excreted formic acid as a potential indicator of adverse growth conditions, while the magnitude of FAME variation between conditions may point to strains with broader substrate tolerance. These findings suggest that methanotroph strains must be carefully evaluated before use in industry, both to identify optimal conditions and to ensure the strain selected is appropriate for the process of interest. As a result, much work remains in addressing the optimization of growth strategies for these promising microorganisms since disregarding these important steps in process development could ultimately lead to inefficient or failed bioprocesses.« less

Authors:

Tays, Catherine ^[1]; Guarnieri, Michael T.  ^[2];

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Sauvageau, Dominic ^[1]; Stein, Lisa Y. ^[1]

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+ Show Author Affiliations

1. Univ. of Alberta, Edmonton, AB (Canada)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States)

Publication Date:

2018-09-25

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE)

OSTI Identifier:

1479279

Report Number(s):

NREL/JA-5100-72672
Journal ID: ISSN 1664-302X

Grant/Contract Number:  

AC36-08GO28308

Resource Type:

Journal Article: Accepted Manuscript

Journal Name:

Frontiers in Microbiology

Additional Journal Information:

Journal Volume: 9; Journal ID: ISSN 1664-302X

Publisher:

Frontiers Research Foundation

Country of Publication:

United States

Language:

English

Subject:

09 BIOMASS FUELS; methanotrophic bacteria; methane; methanol; ammonium; nitrate; FAME