Improvement of 1,3-Propanediol Production From Crude Glycerol by Co-cultivation of Anaerobic and Facultative Microbes Under Non-strictly Anaerobic Conditions

Background: Natural microbial consortia could efficiently produce 1,3-propanediol, the most promising bulk biochemical derived from glycerol that can be used as a monomer in the synthesis of polytrimethylene terephthalate (PTT). While natural microbial communities are made up of a diverse range of microbes with frequently unknown functions, the construction of synthetic microbial consortia allows for creating more defined systems with lower complexity.Results: In this study, the synthetic microbial consortia were constructed by combing facultative microbes of Klebsiella pneumoniae DUT2 (KP) and/or Escherichia coli DUT3 (EC) cultures with the strict anaerobic microbe of Clostridium butyricum DUT1 (CB) cultures under micro-aerobic conditions. The function of EC and KP during the fermentation process was to deplete oxygen and provide an anaerobic environment for CB. Furthermore, KP competes with CB to consume crude glycerol and produce 1,3-PDO. The interaction of commensalism and competition resulted in synthetic microbial consortia that could efficiently convert crude glycerol to 1,3-PDO even under micro-aerobic conditions. In a batch fermentation, the synthetic CB:KP co-culture at an initial abundance ratio of 92.5:7.5 yielded a maximum 1,3-PDO concentration of 52.08 g/L, with a yield of 0.49 g/g and a productivity of 1.80 g/(L.h), which increased by 10%, 9%, and 12%, respectively, when compared to the CB mono-culture under strictly anaerobic conditions. Compared to the KP mono-culture, the final 1,3-PDO concentration, yield, and productivity by the synthetic CB:KP consortia increased by 16%, 19%, and 84%, respectively. The synthetic CB:KP:EC co-culture achieved the highest 1,3-PDO flux of 49.17% at an initial abundance ratio of 85:7.5:7.5, while 7.43%, 5.77%, 3.15% 4.24%, and 2.13% of flux was distributed to butyric acid, acetic acid, lactic acid, ethanol, and succinic acid pathways. In a fed-batch fermentation, synthetic CB:KP:EC co-culture demonstrated a maximum 1,3-PDO concentration of 77.68 g/L with a yield of 0.51 g/g which is 30% and 13% higher than the production by the CB mono-culture at 0.02 vvm N2 supply. The initial abundance of CB guaranteed to be at least 85% facilitates 1,3-PDO production from crude glycerol efficiently by the development of synthetic microbial consortia. Conclusion: Under micro-aerobic conditions, the synthetic microbial consortia demonstrated excellent performance on 1,3-propanediol production via the interaction of commensalism and competition. The experimental results demonstrated the potential benefit of using the synthetic microbial consortia to produce 1,3-propanediol from crude glycerol.

Annulment of antagonism shifts properties that are beneficial to plants in two-member consortia of Bacillus velezensis

Bacillus spp. strains that are beneficial to plants are widely used in commercial biofertilizers and biocontrol agents for sustainable agriculture. Generally, functional Bacillus strains are applied as single strain communities since the principles of synthetic microbial consortia constructed with Bacillus strains remain largely unclear. Here, we demonstrated that the mutual compatibility directly affects the survival and function of two-member consortia composed of B. velezensis SQR9 and FZB42 in the rhizosphere. A mutation in the global regulator Spo0A of SQR9 markedly reduced the boundary phenotype with wild-type FZB42, and the combined use of the SQR9Δspo0A mutant and FZB42 improved biofilm formation, root colonization and the production of secondary metabolites that are beneficial to plants. We further confirmed the correlation between the swarm discrimination phenotype between the two consortia members and the effects that are beneficial to plants in a greenhouse experiment. Our results provide evidence that social interactions among bacteria could be an influencing factor in achieving a desired community-level function.

Bacillus subtilis Chassis in Biomanufacturing 4.0

Synthetic biology, an emerging research field, can promote biomanufacturing by offering various efficient chassis. Engineering Bacillus subtilis, an important workhorse in industrial biotechnology, through synthetic biology approaches may be a disruptive innovation. Advancements in chassis engineering, a synthetic biology strategy for genome-reduced cell factories, cell-free systems, and synthetic microbial consortia would be a driving force facilitating microbial production. We discussed chassis engineering categories and applications for B. subtilis. Prospects and challenges for chassis engineering in B. subtilis were also analyzed in this review article.

Harnessing microbial wealth for lignocellulose biomass valorization through secretomics: a review

The recalcitrance of lignocellulosic biomass is a major constraint to its high-value use at industrial scale. In nature, microbes play a crucial role in biomass degradation, nutrient recycling and ecosystem functioning. Therefore, the use of microbes is an attractive way to transform biomass to produce clean energy and high-value compounds. The microbial degradation of lignocelluloses is a complex process which is dependent upon multiple secreted enzymes and their synergistic activities. The availability of the cutting edge proteomics and highly sensitive mass spectrometry tools make possible for researchers to probe the secretome of microbes and microbial consortia grown on different lignocelluloses for the identification of hydrolytic enzymes of industrial interest and their substrate-dependent expression. This review summarizes the role of secretomics in identifying enzymes involved in lignocelluloses deconstruction, the development of enzyme cocktails and the construction of synthetic microbial consortia for biomass valorization, providing our perspectives to address the current challenges.

Dynamics of diffusive cell signaling relays

In biological contexts as diverse as development, apoptosis, and synthetic microbial consortia, collections of cells or subcellular components have been shown to overcome the slow signaling speed of simple diffusion by utilizing diffusive relays, in which the presence of one type of diffusible signaling molecule triggers participation in the emission of the same type of molecule. This collective effect gives rise to fast-traveling diffusive waves. Here, in the context of cell signaling, we show that system dimensionality – the shape of the extracellular medium and the distribution of cells within it – can dramatically affect the wave dynamics, but that these dynamics are insensitive to details of cellular activation. As an example, we show that neutrophil swarming experiments exhibit dynamical signatures consistent with the proposed signaling motif. We further show that cell signaling relays generate much steeper concentration profiles than does simple diffusion, which may facilitate neutrophil chemotaxis.