Screening of Bacterial Isolates with Probiotic Potential of Tiger Nut Drink, Ogi and Palm Wine

Probiotics are live microorganisms that are very beneficial to human health when consumed in a sufficient amount. Screening and fingerprinting of isolates with probiotic potentials from indigenous food products were evaluated. Fresh palm wine, Ogi and Tiger nut drinks were bought from retailers in Obio-Akpor and Port Harcourt Local Government Area, Rivers State. These samples on getting to the lab in sterile containers were analysed using standard microbiological techniques for the enumeration and isolation of bacterial isolates. Identification of isolates relied on the biochemical and genomic techniques using standard methods. The probiotics were screened based on their ability to tolerate ethanol, bile salt, low pH, high salt concentration, lactose utilization and the production of biogenic amine. Antimicrobial susceptibility of the bacterial isolates (probiotics) was carried out using the Kirby-Bauer disc diffusion. Forty-two bacterial isolates which belonged to the genera: Lactobacillus sp, Pediococcus sp, Enterococcus sp and Streptococcus sp were identified. Genomic characterization of isolates showed that isolate NO2 has 83.4% pairwise identity with Bacillus firmus strain T1, Isolate NP2 has 86.5% pairwise identity with Bacillus cereus strain PKID1, NT8 has 80.3% pairwise identity with Bacillus cereus strain PV-G21. Results of screened probiotics showed that out of the forty-two bacterial isolates, only fifteen were non-spore producers and that they were tolerant to ethanol, low pH, NaCl and bile salt at all concentrations. Results of lactose utilization showed that only twelve out of the fifteen bacterial isolates utilized lactose. Results of biogenic amine production showed that only five out of fifteen bacterial isolates produced biogenic amine. The antibiotic susceptibility pattern of the screened bacterial isolates showed that they exhibited resistance to Pefloxacin, Gentamycin, Ampiclox, Amoxicillin, Rocephin, Ciprofloxacin; Streptomycin, Sceptrin and Erythromycin. They were highly resistant to Gentamycin and Zinnacef. Bacillus firmus strain T1, Bacillus cereus strain PKID1 and Bacillus cereus strain PV-G21 were identified as bacterial probiotics. Consumption of palm wine, Ogi and tiger nut drinks is highly recommended due to the availability of probiotics.

Upcycling of Whey Permeate through Yeast- and Mold-Driven Fermentations under Anoxic and Oxic Conditions

Dairy manufacturing generates whey by-products, many of them considered waste; others, such as whey permeate, a powder high in lactose and minerals from deproteinated whey, have unrealized potential. This study identified yeast species capable of utilizing lactose from whey permeate to produce ethanol or organic acids, and identified fungal species that reduced the acidity of whey by-products. Reconstituted whey permeate was fermented anaerobically or aerobically for 34 days, using species from Cornell University’s Food Safety Lab, Alcaine Research Group, and Omega Labs. Yeast species: Kluyveromyces marxianus, Kluyveromyces lactis, Dekkera anomala, Brettanomyces claussenii, Brettanomyces bruxellensis; mold species: Mucor genevensis and Aureobasidium pullulans. Density, pH, cell concentrations, organic acids, ethanol, and sugar profiles were monitored. Under anoxic conditions, K. marxianus exhibited the greatest lactose utilization and ethanol production (day 20: lactose non-detectable; 4.52% ± 0.02 ethanol). Under oxic conditions, D. anomala produced the most acetic acid (day 34: 9.18 ± 3.38 g/L), and A. pullulans utilized the most lactic acid, increasing the fermentate’s pH (day 34: 0.26 ± 0.21 g/L, pH: 7.91 ± 0.51). This study demonstrates that fermentation of whey could produce value-added alcoholic or organic acid beverages, or increase the pH of acidic by-products, yielding new products and increasing sustainability.

Influence of L-lactate and low glucose concentrations on the metabolism and the toxin formation of Clostridioides difficile

The virulence of Clostridioides difficile (formerly Clostridium difficile) is mainly caused by its two toxins A and B. Their formation is significantly regulated by metabolic processes. Here we investigated the influence of various sugars (glucose, fructose, mannose, trehalose), sugar derivatives (mannitol and xylitol) and L-lactate on toxin synthesis. Fructose, mannose, trehalose, mannitol and xylitol in the growth medium resulted in an up to 2.2-fold increase of secreted toxin. Low glucose concentration of 2 g/L increased the toxin concentration 1.4-fold compared to growth without glucose, while high glucose concentrations in the growth medium (5 and 10 g/L) led to up to 6.6-fold decrease in toxin formation. Transcriptomic and metabolic investigation of the low glucose effect pointed towards an inactive CcpA and Rex regulatory system. L-lactate (500 mg/L) significantly reduced extracellular toxin formation. Transcriptome analyses of the later process revealed the induction of the lactose utilization operon encoding lactate racemase (larA), electron confurcating lactate dehydrogenase (CDIF630erm_01321) and the corresponding electron transfer flavoprotein (etfAB). Metabolome analyses revealed L-lactate consumption and the formation of pyruvate. The involved electron confurcation process might be responsible for the also observed reduction of the NAD+/NADH ratio which in turn is apparently linked to reduced toxin release from the cell.

Efficient 2,3-butanediol production from whey powder using metabolically engineered Klebsiella oxytoca

Background: Whey is a major pollutant generated by the dairy industry. To decrease environmental pollution caused by the industrial release of whey, new prospects for its utilization need to be urgently explored. Here, we investigated the possibility of using whey powder to produce 2,3-butanediol (BDO), an important platform chemical. Results: Klebsiella oxytoca strain PDL-0 was selected because of its ability to efficiently produce BDO from lactose, the major fermentable sugar in whey. After deleting genes pox , pta , frdA , ldhD , and pflB responding for the production of by-products acetate, succinate, lactate, and formate, a recombinant strain K. oxytoca PDL-K5 was constructed. Fed-batch fermentation using K. oxytoca PDL-K5 produced 74.9 g/L BDO with a productivity of 2.27 g/L/h and a yield of 0.43 g/g from lactose. In addition, when whey powder was used as the substrate, 65.5 g/L BDO was produced within 24 h with a productivity of 2.73 g/L/h and a yield of 0.44 g/g. Conclusion: This study demonstrated the efficiency of K. oxytoca PDL-0 for BDO production from whey. Due to its non-pathogenicity and efficient lactose utilization, K. oxytoca PDL-0 might also be used in the production of other important chemicals using whey as the substrate.

Efficient Production of 2,3-Butanediol from whey Powder by Metabolic Engineered Klebsiella Oxytoca

Backgrounds: Whey is the major pollution source from the dairy industry. Exploring new outlets for whey utilization is urgently needed to decline its environmental pollution. In this study, we explored the possibility of using whey powder to produce 2,3-butanediol (2,3-BD), an important platform chemical.Results: A Klebsiella oxytoca strain PDL-0 was selected from five 2,3-BD producing strains based on its ability to efficiently produce 2,3-BD from lactose, the major fermentable sugar in whey. Five genes including pox, pta, frdA, ldhD, and pflB were knocked out in K. oxytoca PDL-0 to decrease the production of byproducts like acetate, succinate, lactate, and formate. Using fed-batch fermentation of K. oxytoca PDL-0 ΔpoxΔptaΔfrdAΔldhDΔpflB, 74.9 g/L 2,3-BD was produced with a productivity of 2.27 g/L/h and a yield of 0.43 g/g from lactose. In addition, when whey powder was used as the substrate, 65.5 g/L 2,3-BD was produced within 24 h with a productivity of 2.73 g/L/h and a yield of 0.44 g/g.Conclusion: This study proved the efficiency of K. oxytoca PDL-0 to metabolize whey for 2,3-BD production. Due to its characteristics of non-pathogenicity and efficient lactose utilization, K. oxytoca PDL-0 might also be used in the production of other important chemicals using whey as the substrate.