Title: Propionic acid production from corn stover hydrolysate by Propionibacterium acidipropionici

Abstract

The production of value-added chemicals alongside biofuels from lignocellulosic hydrolysates is critical for developing economically viable biorefineries. Here, the production of propionic acid (PA), a potential building block for C3-based chemicals, from corn stover hydrolysate is investigated using the native PA-producing bacterium Propionibacterium acidipropionici. A wide range of culture conditions and process parameters were examined and experimentally optimized to maximize titer, rate, and yield of PA. The effect of gas sparging during fermentation was first examined, and N₂ was found to exhibit improved performance over CO₂. Subsequently, the effects of different hydrolysate concentrations, nitrogen sources, and neutralization agents were investigated. One of the best combinations found during batch experiments used yeast extract (YE) as the primary nitrogen source and NH₄OH for pH control. This combination enabled PA titers of 30.8 g/L with a productivity of 0.40 g/L h from 76.8 g/L biomass sugars, while successfully minimizing lactic acid production. Due to the economic significance of downstream separations, increasing titers using fed-batch fermentation was examined by changing both feeding media and strategy. Continuous feeding of hydrolysate was found to be superior to pulsed feeding and combined with high YE concentrations increased PA titers to 62.7 g/L and improved the simultaneous utilizationmore » of different biomass sugars. Additionally, applying high YE supplementation maintains the lactic acid concentration below 4 g/L for the duration of the fermentation. Finally, with the aim of increasing productivity, high cell density fed-batch fermentations were conducted. PA titers increased to 64.7 g/L with a productivity of 2.35 g/L h for the batch stage and 0.77 g/L h for the overall process. These results highlight the importance of media and fermentation strategy to improve PA production. Altogether, this work demonstrates the feasibility of producing PA from corn stover hydrolysate.« less

Authors:

Wang, Xiaoqing; Salvachúa, Davinia; Sànchez i Nogué, Violeta; Michener, William E.; Bratis, Adam D.; Dorgan, John R.; Beckham, Gregg T.

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Publication Date:

Thu Aug 17 00:00:00 EDT 2017

Research Org.:

National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Bioenergy Technologies Office

OSTI Identifier:

1618686

Alternate Identifier(s):

OSTI ID: 1379461

Report Number(s):

NREL/JA-5100-70061
Journal ID: ISSN 1754-6834; 200; PII: 884

Grant/Contract Number:  

FOA-0000996; AC36-08GO28308

Resource Type:

Published Article

Journal Name:

Biotechnology for Biofuels

Additional Journal Information:

Journal Name: Biotechnology for Biofuels Journal Volume: 10 Journal Issue: 1; Journal ID: ISSN 1754-6834

Publisher:

Springer Science + Business Media

Country of Publication:

Netherlands

Language:

English

Subject:

09 BIOMASS FUELS; lignocellulosic biomass; fermentation; biochemicals; biorefinery; organic acids