Metabolism, morphology and transcriptome analysis of oscillatory behavior of Clostridium butyricum during long-term continuous fermentation for 1,3-propanediol production

Abstract

Background Oscillation is a special cell behavior in microorganisms during continuous fermentation, which poses threats to the output stability for industrial productions of biofuels and biochemicals. In previous study, a spontaneous oscillatory behavior was observed in Clostridium butyricum-intensive microbial consortium in continuous fermentation for 1,3-propanediol (1,3-PDO) production from glycerol, which led to the discovery of oscillation in species C. butyricum. Results Spontaneous oscillations by C. butyricum tended to occur under glycerol-limited conditions at low dilution rates. At a glycerol feed concentration of 88 g/L and a dilution rate of 0.048 h−1, the oscillatory behavior of C. butyricum was observed after continuous operation for 146 h and was sustained for over 450 h with an average oscillation period of 51 h. During oscillations, microbial glycerol metabolism exhibited dramatic periodic changes, in which productions of lactate, formate and hydrogen significantly lagged behind that of other products including biomass, 1,3-PDO and butyrate. Analysis of extracellular oxidation–reduction potential and intracellular ratio of NAD+/NADH indicated that microbial cells experienced distinct redox changes during oscillations, from oxidized to reduced state with decreasing of growth rate. Meanwhile, C. butyricum S3 exhibited periodic morphological changes during oscillations, with aggregates, elongated shape, spores or cell debris at the trough of biomass production. Transcriptome analysis indicated that expression levels of multiple genes were up-regulated when microbial cells were undergoing stress, including that for pyruvate metabolism, conversion of acetyl-CoA to acetaldehyde as well as stress response. Conclusion This study for the first time systematically investigated the oscillatory behavior of C. butyricum in aspect of occurrence condition, metabolism, morphology and transcriptome. Based on the experimental results, two hypotheses were put forward to explain the oscillatory behavior: disorder of pyruvate metabolism, and excessive accumulation of acetaldehyde.

High level of 1,3‐propanediol production from crude glycerol by Clostridium strain BOH3: critical roles of inoculum and substrate concentration

“…Likewise, the operational temperature of a fermentation can directly influence the rate of cellular growth and several enzymes involved in the metabolic pathways. Consequently, the bioconversion of substrate into cell biomass and distribution of various metabolic products can be modulated 56,58,59 . In the case of PDO production from CG fermentation by Clostridia , the effects of initial medium‐pH and operational temperature are yet to be investigated.…”

“…Consequently, the bioconversion of substrate into cell biomass and distribution of various metabolic products can be modulated. 56,58,59 In the case of PDO production from CG fermentation by Clostridia, the effects of initial medium-pH and operational temperature are yet to be investigated. However, a slight acidic to neutral pH between pH 6.5 and 7.0, with the operational temperature between 32 and 37 °C were suggested for CG fermentation by Clostridium strains including C. butyricum VPI 1718, 1 E4-5, 32 DSP1, 4 AKR102a 18 and VPI 3266.…”

Visible-Light-Driven Enhanced Biohydrogen Production by Photo-Biohybrid System Based on Photoelectron Transfer between Intracellular Photosensitizer Gold Nanoparticles and Clostridium butyricum

“…Transcriptome test results showed that compared with the dark fermentation biohybrid system, the expression of lactate dehydrogenase in PBS was upregulated by 2.07-fold, corresponding to the increase of lactic acid accumulation in PBS. It is speculated that after the photogenerated electrons of PBS participate in biohydrogen production, the excess electrons participate in the consumption of reducing the force in lactic acid metabolism to ensure the balance of cell redox metabolism. , The expression of genes for key enzymes in butyrate metabolism ( hbd , crtI , buk ) and genes for key enzymes in acetate metabolism ( pta , ack ) all did not receive significant effects from Au NPs and light exposure, making the butyrate and acetate of PBS only weakly reduce (no significant difference) compared with those of the naked C. butyricum (Figure b).…”

In situ carbon dioxide capture to co-produce 1,3-propanediol, biohydrogen and micro-nano calcium carbonate from crude glycerol by Clostridium butyricum

“…During the microbial fermentation of 1,3-PDO, organic acids were produced as by-products, as well as CO 2 as exhaust gas, due to redox homeostasis and energy balance during the glycerol metabolism [ 25 , 49 , 50 ]. As a CO 2 capture agent and pH regulator, NaOH was selected to absorb CO 2 and neutralize the organic acids, e.g., 5 M NaOH solution used for anaerobic fermentations by C. butyricum DL07.…”