High-Rate Production of Short-Chain Fatty Acids from Methane in a Mixed-Culture Membrane Biofilm Reactor

Abstract

The bioconversion of methane to liquid chemicals has attracted much attention. However, the production rate reported to date has been far lower than what is required for economical viability. This is partly due to the low solubility of methane, the low mass transfer rate, and low microbial activities. This study demonstrates a production rate of close to 10 g of short-chain fatty acids (SCFAs) per liter per day with a mixed-culture biofilm growing in a membrane biofilm reactor (MBfR). Hollow fiber membranes were used both to deliver a high flux of methane and to provide a surface on which slow-growing microorganisms could form biofilms with intensified activities. The rate achieved is nearly 2 orders of magnitude higher than the highest SCFA production rate reported to date and is close to the rates required for practical applications (∼12−120 g L −1 day −1 ). The consortium in the biofilm was dominated by methanogens Methanosarcina and Methanobacterium and acid-producing bacteria Sporolactobacillus and Propionispora, suggesting likely roles of these organisms in the bioconversion of methane into SCFAs. This work shows a methane-based MBfR represents a promising technology for achieving high-rate production of chemicals from methane.

Enhancing methane oxidation in a bioelectrochemical membrane reactor using a soluble electron mediator

“…Bubble-less gas exchange HFMs have been shown as effective for delivering gaseous substrate of CH 4 because CH 4 can be delivered directly from the inside of HFMs to a biofilm attached on the outer surface of HFMs [21,28]. Thus, colonization of a CH 4 -oxidizing biofilm on HFMs is the prerequisite for a highly efficient CH 4 utilization system.…”

Enhanced Methane Recovery from Waste-Activated Sludge by Alginate-Degrading Consortia: The Overlooked Role of Alginate in Extracellular Polymeric Substances

“…The disposal of waste-activated sludge (WAS) is an environmental problem that can be expensive, as it consumes up to 50% of the total operating cost of wastewater treatment plants. , Anaerobic digestion is an important biotechnology that can stabilize and reduce volatile solids while recovering bioenergy as methane. , Polysaccharides (including neutral sugars and uronic acids) and proteins are the main components of extracellular polymeric substances (EPS) in WAS . WAS hydrolysis is considered as the rate-limiting step in anaerobic digestion, which is mainly caused by difficult-to-degrade EPS. , Various pretreatment technologies, including mechanical, thermal, and chemical methods, have been proposed to enhance the hydrolysis process, , which increases the operating cost for WAS treatment.…”

“…1,2 Anaerobic digestion is an important biotechnology that can stabilize and reduce volatile solids while recovering bioenergy as methane. 3,4 Polysaccharides (including neutral sugars and uronic acids) and proteins are the main components of extracellular polymeric substances (EPS) in WAS. 5 WAS hydrolysis is considered as the rate-limiting step in anaerobic digestion, which is mainly caused by difficult-todegrade EPS.…”

Membrane bioreactors for syngas permeation and fermentation

“…In these systems, liquid mixing can be achieved by using a microporous membrane as a gas micro-diffuser, designated as a hollow fiber membrane bubble column reactor (HFM-BCR) [43,44]. This is also achieved by the implementation of impellers in the reactor [55], or the addition of a liquid recirculation circuit [10,59].…”

“…Nonvolatile products are collected from the tank effluent. For simplicity, laboratory setups can use an overflow bottle as the external reservoir [59]. Both configurations have been tested in liquid batch, in sequential batch, or continuous configuration mode (Table 5).…”