Corynebacterium glutamicum has been considered a promising synthetic biological platform for biomanufacturing and bioremediation. However, there are still some challenges in genetic manipulation of C. glutamicum. Recently, more and more genetic parts or elements (replicons, promoters, reporter genes, and selectable markers) have been mined, characterized, and applied. In addition, continuous improvement of classic molecular genetic manipulation techniques, such as allelic exchange via single/double-crossover, nuclease-mediated site-specific recombination, RecT-mediated single-chain recombination, actinophages integrase-mediated integration, and transposition mutation, has accelerated the molecular study of C. glutamicum. More importantly, emerging gene editing tools based on the CRISPR/Cas system is revolutionarily rewriting the pattern of genetic manipulation technology development for C. glutamicum, which made gene reprogramming, such as insertion, deletion, replacement, and point mutation, much more efficient and simpler. This review summarized the recent progress in molecular genetic manipulation technology development of C. glutamicum and discussed the bottlenecks and perspectives for future research of C. glutamicum as a distinctive microbial chassis.

Biofuel consists of non-fossil fuel derived from the organic biomass of renewable resources, including plants, animals, microorganisms, and waste. Energy derived from biofuel is known as bioenergy. The reserve of fossil fuels is now limited and continuing to decrease, while at the same time demand for energy is increasing. In order to overcome this scarcity, it is vital for human beings to transfer their dependency on fossil fuels to alternative types of fuel, including biofuels, which are effective methods of fulfilling present and future demands. The current review therefore focusses on second-generation lignocellulosic biofuels obtained from non-edible plant biomass (i.e., cellulose, lignin, hemi-celluloses, non-food material) in a more sustainable manner. The conversion of lignocellulosic feedstock is an important step during biofuel production. It is, however, important to note that, as a result of various technical restrictions, biofuel production is not presently cost efficient, thus leading to the need for improvement in the methods employed. There remain a number of challenges for the process of biofuel production, including cost effectiveness and the limitations of various technologies employed. This leads to a vital need for ongoing and enhanced research and development, to ensure market level availability of lignocellulosic biofuel.

The solventogenic clostridia have a considerable capacity to ferment carbohydrate substrates with the production of acetone and butanol, making them attractive organisms for the conversion of waste materials to valuable products. In common with other anaerobes, the clostridia show a marked dependence on the phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) to accumulate sugars and sugar derivatives. In this study, we demonstrate that extracts of Clostridium beijerinckii grown on N-acetylglucosamine (GlcNAc) exhibit PTS activity for the amino sugar. The PTS encoded by the divergent genes cbe4532 (encoding the IIC and IIB domains) and cbe4533 (encoding a IIA domain) was shown to transport and phosphorylate GlcNAc and also glucose. When the genes were recombined in series under the control of the lac promoter in pUC18 and transformed into a phosphotransferase mutant (nagE) of Escherichia coli lacking GlcNAc PTS activity, the ability to take up and ferment GlcNAc was restored, and extracts of the transformant showed PEP-dependent phosphorylation of GlcNAc. The gene products also complemented an E. coli mutant lacking glucose PTS activity but were unable to complement the same strain for PTS-dependent mannose utilization. Both GlcNAc and glucose induced the expression of cbe4532 and cbe4533 in C. beijerinckii, and consistent with this observation, extracts of cells grown on glucose exhibited PTS activity for GlcNAc, and glucose did not strongly repress utilization of GlcNAc by growing cells. On the basis of the phylogeny and function of the encoded PTS, we propose that the genes cbe4532 and cbe4533 should be designated nagE and nagF, respectively.T he acetone-butanol-ethanol (ABE) fermentation of Clostridium acetobutylicum and related bacteria has a successful history of industrial-scale operation worldwide but went into decline during the latter part of the 20th century for economic reasons (1). Nevertheless, stimulated by concerns relating to the environmental effects of burning fossil fuels and the potential of butanol as a biofuel, interest in this fermentation is being revived (2). Traditionally, the industrial process used starch or molasses as the fermentable substrate, and while these may still be employed, the fermentation of the future is likely to be based on a variety of alternative feedstocks that are derived as waste products from other processes. Lignocellulose-based agricultural waste poducts have attracted considerable attention, but other materials are also being considered (3, 4). An important criterion is that the fermentable substrates should be effectively utilized to support high productivity, yield, and titer of the desired metabolic end product.The solventogenic clostridia are capable of utilizing a wide range of carbohydrate substrates, thus displaying a metabolic capability that can be harnessed for the development of fermentation processes (5). In common with other obligately anaerobic bacteria, the principal mechanism of accumulation of fermentable monosaccharides, disac...

Short- and medium-chain volatile esters with flavors and fruity fragrances, such as ethyl acetate, butyl acetate, and butyl butyrate, are usually value-added in brewing, food, and pharmacy. The esters can be naturally produced by some microorganisms. As ester-forming reactions are increasingly deeply understood, it is possible to produce esters in non-natural but more potential hosts. Clostridia are a group of important industrial microorganisms since they can produce a variety of volatile organic acids and alcohols with high titers, especially butanol and butyric acid through the CoA-dependent carbon chain elongation pathway. This implies sufficient supplies of acyl-CoA, organic acids, and alcohols in cells, which are precursors for ester production. Besides, some Clostridia could utilize lignocellulosic biomass, industrial off-gas, or crude glycerol to produce other branched or straight-chain alcohols and acids. Therefore, Clostridia offer great potential to be engineered to produce short- and medium-chain volatile esters. In the review, the efforts to produce esters from Clostridia via in vitro lipase-mediated catalysis and in vivo alcohol acyltransferase (AAT)-mediated reaction are comprehensively revisited. Besides, the advantageous characteristics of several Clostridia and clostridial consortia for bio-ester production and the driving force of synthetic biology to clostridial chassis development are also discussed. It is believed that synthetic biotechnology should enable the future development of more effective Clostridia for ester production.

The ubiquitous presence of pharmaceutical drugs and microbes in the water is leading to the development of drug resistant microbes. Therefore, efficient materials that can remove or inactivate the drug and microbe contaminants are required. In this work, nickel sulfide/calcium alginate (Ni3S4/CA), silver sulfide/calcium alginate (Ag2S/CA), modified titanium dioxide/calcium alginate (TiO2/CA), and Ni3S4/Ag2S/TiO2/calcium alginate (Ni3S4/Ag2S/TiO2/CA) aerogels have been synthesized for the removal of the oxytetracycline (OTC) drug and microbial contaminants from real beverage industry wastewater. The results revealed that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient for OTC adsorption and inactivation of microbes compared to Ni3S4/CA, Ag2S/CA and TiO2/CA aerogels. The OTC adsorption depends greatly on the solution pH, and optimum OTC removal was observed at pH 6 in its zwitterionic (OTC±) form. The formation of H-bonding and n-π electron donor-acceptors is possible to a considerable extent due to the presence of the double bond benzene ring, oxygen and nitrogen, sulfur-containing functional groups on the OTC molecules, and the Ni3S4/Ag2S/TiO2/CA aerogel. Based on the statistical analysis, root-mean-square deviation (RMSD), chi square (χ2) values, and higher correlation coefficient (R2) values, the Redlich–Peterson isotherm model and Elovich kinetic model are most suited to modelling the OTC adsorption onto Ni3S4/Ag2S/TiO2/CA. The prepared aerogels’ excellent antimicrobial activity is observed in the dark and with solar light irradiation. The zone of inhibition analysis revealed that the antimicrobial activity of the aerogels is in the following order: Ni3S4/Ag2S/TiO2/CA > TiO2/CA > Ag2S/CA > Ni3S4/CA, respectively. Moreover, the antimicrobial results demonstrated that reactive oxygen species, electrons, and active radical species are responsible for growth inhibition and killing of the microbes. These results indicated that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient in decontaminating pollutants from wastewater.