Use of oxidoreduction potential as an indicator to regulate 1,3-propanediol fermentation by Klebsiella pneumoniae

Abstract

Anaerobic fermentation was relatively difficult to optimize due to lack of monitoring parameters. In this paper, a new method was reported using extracellular oxidoreduction potential (ORP) to monitor 1,3-propanediol (1,3-PD) biosynthesis process by Klebsiella pneumoniae. In batch fermentation, cell growth, 1,3-propanediol production and by-products distribution were studied at four different ORP levels: 10, -140, -190 and -240 mV. From the results, the ORP level of -190 mV was preferable, which resulted in fast cell growth and high 1,3-propanediol concentration. The NAD+/NADH ratio was determined at different ORP levels, and a critical NAD+/NADH ratio of 4 was defined to divide fermentation environments into two categories: relatively oxidative environment (NAD+/NADH>4) and relatively reductive environment (NAD+/NADH<4). The former was correlative with high 1,3-propanediol productivity and high specific growth rate. The mechanism of ORP regulation was discussed. It is suggested that ORP regulation of fermentation might be due to its influence on the ratio of NAD+/NADH, which determined metabolic flux. Furthermore, a batch fermentation of modulating ORP following a profile in different levels corresponding to different fermentation stage was tested. The 1,3-PD concentration was 22.3% higher than that of constant ORP fermentation at -190 mV. Therefore, ORP is a valuable parameter to monitor and control anaerobic fermentation production.

Metabolic Process Engineering for Biochemicals and Biofuels Production

“…Robust, fast response, precise and in situ probes can partially solve this issue by providing online sample analysis. Some sensors, including biomass probe, dissolved oxygen probe, extracellular oxidoreduction potential probe, and gas monitors, are used in fermentation to monitor cell growth, assess aerobic metabolism, estimate NAD + /NADH + ratio, and measure gases (e.g., CO 2 , CH 4 and H 2 ), respectively [4].In addition, biochemical analysers connected to auto-samplers are used for online monitoring of multiple metabolites. Different from discrete sensors, the MS based chemical multisensory systems, named as electronic noses and electronic tongues [5], have been used in both qualitative recognition of multi-component media and quantitative analysis of component concentrations in wine production.…”

Metabolic Changes in Klebsiella oxytoca in Response to Low Oxidoreduction Potential, as Revealed by Comparative Proteomic Profiling Integrated with Flux Balance Analysis

“…Decreased ORP levels also improved the xylitol yield of stationary-phase fermentation by Candida tropicalis (19). Therefore, the extracellular ORP is a useful parameter for monitoring and regulating microbial metabolism in anaerobic or microaerobic processes (4,12,13,(19)(20)(21)(22)24).However, the physiological response of microbial cells to ORP alterations remains unclear. ORP changes may affect cellular physiology by altering intracellular redox levels (4), affecting the expression of individual enzymes (16,25) and changing the oxidative states of protein thiol groups.…”

“…The ORP quantifies the redox property of solutions (11) and is a primary affecter of (facultative) anaerobic growth and metabolism (4,(12)(13)(14)(15)(16)(17). Generally, each microbial species optimally grows within a certain ORP range (14-16), and alteration of extracellular ORP usually leads to metabolic flux redistribution.…”

“…Decreased ORP levels also improved the xylitol yield of stationary-phase fermentation by Candida tropicalis (19). Therefore, the extracellular ORP is a useful parameter for monitoring and regulating microbial metabolism in anaerobic or microaerobic processes (4,12,13,(19)(20)(21)(22)24).…”

“…This preculture was inoculated (5% [vol/vol]) into a 300-ml flask containing 100 ml chemically defined medium (4) and cultured anaerobically (nitrogen in headspace, 35°C, 120 rpm, 24 h) at pH ϳ7.0 (buffered by adding calcium carbonate). The anaerobic flask culture was then inoculated (10% [vol/vol]) into a 7-liter BioFlo110 fermenter (New Brunswick Scientific, Edison, NJ) equipped with an ORP Automatic Controlling System (30) to initiate anaerobic fermentation (nitrogen in headspace, 35°C, 400 rpm, 66 h), with an initial working volume of 3.0 liter.…”