Valorization of lignocellulosic biomass (LB) has the potential to secure sustainable energy production without impacting food insecurity, whist relieving over reliance on finite fossil fuels. Agro-derived lignocellulosic residues such as wheat straw, switchgrass, rice bran, and miscanthus have gained relevance as feedstocks for the production of biofuels and chemicals. However, the microorganisms employed in fermentative conversion of carbohydrates to fuels and chemicals are unable to efficiently utilize the sugars derived from LB due to co-production of lignocellulose-derived microbial inhibitory compounds (LDMICs) during LB pretreatment. LDMICs impact microbial growth by inhibition of specific enzymes, cause DNA and cell membrane damage, and elicit cellular redox imbalance. Over the past decade, success has been achieved with the removal of LDMICs prior to fermentation. However, LDMICs removal by chemical processes is often accompanied by sugar losses, which negatively impacts the overall production cost. Hence, in situ removal of LDMICs by fermentative organisms during the fermentation process has garnered considerable attention as the “go-to” approach for economical LDMICs detoxification and bio-chemicals production. In situ removal of LDMICs has been pursued by either engineering more robust biocatalysts or isolating novel microbial strains with the inherent capacity to mineralize or detoxify LDMICs to less toxic compounds. While some success has been made along this line, efficient detoxification and robust production of target bio-chemicals in lignocellulosic hydrolysates (LHs) under largely anaerobic fermentative conditions remains a lingering challenge. Consequently, LB remains an underutilized substrate for bio-chemicals production. In this review, the impact of microbial LH detoxification on overall target molecule production is discussed. Further, the biochemical pathways and mechanisms employed for in situ microbial detoxification of furanic LDMICs [e.g., furfural and 5-hydroxymethylfurfural (HMF)] and phenolic LDMICs (e.g., syringaldehyde, p-coumaric acid, 4-hydroxybenzaldehyde, vanillin, and ferulic acid) are discussed. More importantly, metabolic engineering strategies for the development of LDMIC-tolerant and bio-chemicals overproducing strains and processes are highlighted.

Efficient bioconversion of abundant waste glycerol to value-added chemicals calls for a wider range of fermentative workhorses that can catabolize glycerol. In this study, we used quantitative gene expression and solvent profiling, qualitative metabolite analysis, and enzyme activity assays to investigate the factors that limit glycerol utilization as a sole carbon source by Clostridium beijerinckii NCIMB 8052. C. beijerinckii NCIMB 8052 did not produce acetate, acetone and butanol on glycerol. Congruently, the genes encoding the coenzyme A transferase subunits (ctfAB) and bifunctional acetaldehyde-CoA/alcohol dehydrogenase (adhE) were down-regulated up to 135- and 21-fold, respectively, at 12 h in glycerol-grown cells compared to glucose-grown cells. Conversely, NADH-dependent butanol dehydrogenase A (bdhA) was upregulated 2-fold. Glycerol dehydrogenase (gldA) and dihydroxyacetone kinase (subunit dhaK) were upregulated up to 5- and 881-fold, respectively. Glyceraldehyde-3-phosphate dehydrogenase (gapdh) showed mostly similar expression profiles at 12 h on glucose and glycerol. At 24 h, gapdh was downregulated 1.5-fold, while NADP⁺-dependent gapdh was upregulated up to 1.9-fold. Glycerol-grown cells showed higher or similar activity profiles for all solventogenic enzymes studied, compared to glucose-grown cells. Butyraldehyde (3 g/L) supplementation led to the production of ~0.1 g/L butanol, whilst butyrate (3.5 g/L) supplementation produced 0.7 and 0.5 g/L acetone and butanol, respectively, with glycerol. Further, the long chain saturated fatty acids cyclopentaneundecanoic acid, methyl ester and hexadecanoic acid, butyl ester were detected in glucose- but not in glycerol-grown cells. Collectively, growth on glycerol appears to disrupt synthesis of saturated long chain fatty acids, as well as solventogenesis in C. beijerinckii NCIMB 8052.

We report the complete genome sequence of Paenibacillus polymyxa DSM 365. The genome consists of a 5,788,318-bp chromosome, with a GC content of 45.48%. Annotation of the genome revealed a total of 5,246 genes (average length, 943 bp). Gene function analysis indicated the ability to fix nitrogen (N ₂ ) and to produce value-added chemicals.

Enterobacter hormaechei is part of the Enterobacter cloacae complex (ECC), which is widespread in nature. It is a facultative Gram-negative bacterium of medical and industrial importance. We assessed the metabolic and genetic repertoires of a new Enterobacter isolate. Here, we report the whole-genome sequence of a furfural- and 5-hydroxymethyl furfural (HMF)-tolerant strain of E. hormaechei (UW0SKVC1), which uses glucose, glycerol, xylose, lactose and arabinose as sole carbon sources. This strain exhibits high tolerance to furfural (IC₅₀ = 34.2 mM; ~3.3 g/L) relative to Escherichia coli DH5α (IC₅₀ = 26.0 mM; ~2.5 g/L). Furfural and HMF are predominantly converted to their less-toxic alcohols. E. hormaechei UW0SKVC1 produces 2,3-butanediol, acetoin, and acetol, among other compounds of industrial importance. E. hormaechei UW0SKVC1 produces as high as ~42 g/L 2,3-butanediol on 60 g/L glucose or lactose. The assembled genome consists of a 4,833,490-bp chromosome, with a GC content of 55.35%. Annotation of the assembled genome revealed 4586 coding sequences and 4516 protein-coding genes (average length 937-bp) involved in central metabolism, energy generation, biodegradation of xenobiotic compounds, production of assorted organic compounds, and drug resistance. E. hormaechei UW0SKVC1 shows considerable promise as a biocatalyst and a genetic repository of genes whose protein products may be harnessed for the efficient bioconversion of lignocellulosic biomass, abundant glycerol and lactose-replete whey permeate to value-added chemicals.

Cholera infection results from the ingestion of water or food contaminated with toxigenic Vibrio cholerae. This study evaluated the occurrence of toxigenic V. cholerae in Asata River, Enugu Metropolis, Nigeria, and estimated V. cholerae infection risks from use of the River water for drinking, domestic and recreational purposes. Vibrio was detected and quantified using membrane filtration technique and thiosulfate–citrate–bile salts–sucrose agar. Isolates were screened by PCR, using specific primers targeting the internal transcribed spacer (its) region between 16 and 23S rRNA and the cholera toxin (ctx) gene. Sequenced 16SrRNA gene amplicons of two selected isolates were used for phylogenetic analysis. Quantitative microbial risk assessment (QMRA) was conducted using the β-Poisson dose–response model. About 81% (58/72) of Asata River samples recorded Vibrio counts above 1.0 $$\times$$× 10³ cfu/100 mL. Of the fifty Vibrio isolates screened, its was detected in 54% (27/50), out of which 74% (20/27) had the ctx gene of toxigenic V. cholerae. Evolutionary relatedness of the sequenced isolates to V. cholerae was revealed. The estimated risks of cholera infection in persons exposed to untreated Asata River water were above 0.5 for all the exposure scenarios, for both the rainy and dry seasons. The risks were highest (~ 0.9) for exposure via drinking water and annual risk of infection was deduced to have a probability of 1.0. Therefore, dependence on the untreated Asata River water for drinking, recreational, domestic and irrigation purposes may present a potential public health risk of cholera outbreak. We recommend increased monitoring and surveillance of River water for Vibrio abundance and that Asata River be protected from further degradation.