Mn(2+) and Mg(2+) synergistically enhanced lactic acid production by Lactobacillus rhamnosus FTDC 8313 via affecting different stages of the hexose monophosphate pathway

Prospective bacterial and fungal sources of hyaluronic acid: A review

The unique biological and rheological properties make hyaluronic acid a sought-after material for medicine and cosmetology. Due to very high purity requirements for hyaluronic acid in medical applications, the profitability of streptococcal fermentation is reduced. Production of hyaluronic acid by recombinant systems is considered a promising alternative. Variations in combinations of expressed genes and fermentation conditions alter the yield and molecular weight of produced hyaluronic acid. This review is devoted to the current state of hyaluronic acid production by recombinant bacterial and fungal organisms.

Co-valorization of corn cobs and dairy wastewater for simultaneous saccharification and lactic acid production: Process optimization and kinetic assessment

This study optimized the co-valorization of corn cob wastes (CCW) and dairy wastewater for simultaneous saccharification and lactic acid (LA) production (sDWW-SSF). Subsequently, the kinetics of Lactobacillus plantarum growth and LA production was assessed using the optimized conditions under microaerophilic (sDWW-SSF_{microaerophilic}) and anaerobic (sDWW-SSF_anaerobic) conditions, and thereafter compared to De Man, Rogosa and Sharpe (MRS) medium modified with pretreated CCW (mMRS-SSF_{microaerophilic}). Optimized sDWW-SSF conditions produced maximum LA concentration and conversion of 11.15 ± 0.42 g/L and 18.90 ± 0.75%, respectively. Kinetic studies revealed that although the mMRS-SSF_{microaerophilic} system obtained a higher maximum specific growth rate (μ_max) and maximum potential LA concentration (P_m) compared to the wastewater-based bioprocesses, the data obtained for the latter were comparable when taking the resources and costs into consideration. These findings represent the potential to eliminate the use of valuable resources in lignocellulosic bioprocesses and provide insights on innovation towards driving a sustainable economy in line with the food-energy-water nexus.

Cloning, purification, and characterization of the 6-phosphogluconate dehydrogenase (6 PGDH) from Giardia lamblia

Giardia lamblia, due to the habitat in which it develops, requires a continuous supply of intermediate compounds that allow it to survive in the host. The pentose phosphate pathway (PPP) provides essential molecules such as NADPH and ribulose-5-phosphate during the oxidative phase of the pathway. One of the key enzymes during this stage is 6-phosphogluconate dehydrogenase (6 PGDH) for generating NADPH. Given the relevance of the enzyme, in the present work, the 6pgdh gene from G. lamblia was amplified and cloned to produce the recombinant protein (Gl-6 PGDH) and characterize it functionally and structurally after the purification of Gl-6 PGDH by affinity chromatography. The results of the characterization showed that the protein has a molecular mass of 54 kDa, with an optimal pH of 7.0 and a temperature of 36-42 °C. The kinetic parameters of Gl-6 PGDH were K_m = 49.2 and 139.9 μM (for NADP⁺ and 6-PG, respectively), Vmax =26.27 μmol*min^-1*mg^-1, and Kcat = 24.0 s^-1. Finally, computational modeling studies were performed to obtain a structural visualization of the Gl-6 PGDH protein. The generation of the model and the characterization assays will allow us to expand our knowledge for future studies of the function of the protein in the metabolism of the parasite.

Optimization of Initial Cation Concentrations for L-Lactic Acid Production from Fructose by Lactobacillus pentosus Cells

In this study, Box-Behnken design was applied to optimize the initial concentrations of 4 cations for L-lactic acid production from fructose by homologous batch fermentation of Lactobacillus pentosus cells. The optimum initial cation concentrations were obtained as 6.542 mM Mg²⁺, 3.765 mM Mn²⁺, 2.397 mM Cu²⁺, and 3.912 mM Fe²⁺, respectively. The highest L-lactic acid yield and productivity were obtained as 0.935 ± 0.005 g/g fructose and 1.363 ± 0.021 g/(L × h), respectively, with a maximum biomass concentration of 7.97 ± 0.17 g/L. The effectiveness of the optimization by Box-Behnken design was confirmed based on the small errors between predicted results and experimental results shown as 0.3%, - 0.2%, and - 1.2%, respectively. The quadratic models with high accuracy and reliability can be applied to mathematically forecasted the fermentation performance. After the optimization, the lactic acid yield and productivity were significantly improved by 3.7% and 21.0%, respectively.

Possibility of L-(+)-lactic acid fermentation using malting, brewing, and oil production by-products

Industrial by-products such as brewer's spent grain (BSG) hydrolysate, malt rootlets extract (MRE) and soybean meal extract (SME) were used for L-(+) lactic acid (LA) production by a pure L. rhamnosus ATCC 7469 strain. The effect of the addition of MRE (10-50%) or SME (10-50%) in BSG hydrolysate on batch and fed-batch LA fermentation was evaluated. The addition of MRE and SME increased the concentration of free amino nitrogen (FAN) and essential minerals (Fe, Mg, Mn, and Zn), which had a positive effect on the fermentation. Also, the MRE addition significantly lowered C/N ration to a more favorable level for the efficient LA fermentation. In batch fermentation, the highest LA concentration (25.73 g/L), yield (86.31%), and volumetric productivity (0.95 g/L h^-1), were obtained with the addition of 50% MRE. Further increase in LA concentration to 58.01 g/L, yield to 88.54%, and volumetric productivity to 1.19 g/L h^-1 was achieved in fed-batch fermentation with addition of 50% MRE. A high optical purity of LA with 99.7% of L-(+)-isomer was obtained on the substrate based on industrial by-products. In addition, solid remains after BSG hydrolysis and MRE and SME preparation, together with the biomass of L. rhamnosus separated after the fermentation could be a good base for feed preparation.

High lactic acid and fructose production via Mn2+-mediated conversion of inulin by Lactobacillus paracasei

Lactobacillus paracasei DSM 23505 is able to produce high amounts of lactic acid (LA) by simultaneous saccharification and fermentation (SSF) of inulin. Aiming to obtain the highest possible amounts of LA and fructose, the present study is devoted to evaluate the impact of bivalent metal ions on the process of inulin conversion. It was shown that Mn2+ strongly increases the activity of the purified key enzyme β-fructosidase. In vivo, batch fermentation kinetics revealed that the high Mn2+ concentrations accelerated inulin hydrolysis by raise of the inulinase activity, and increased sugars conversion to LA through enhancement of the whole glycolytic flux. The highest LA concentration and yield were reached by addition of 15 mM Mn2+-151 g/L (corresponding to 40% increase) and 0.83 g/g, respectively. However, the relative quantification by real-time reverse transcription assay showed that the presence of Mn2+ decreases the expression levels of fosE gene encoding β-fructosidase. Contrariwise, the full exclusion of metal ions resulted in fosE gene expression enhancement, blocked fructose transport, and hindered fructose conversion thus leading to huge fructose accumulation. During fed-batch with optimized medium and fermentation parameters, the fructose content reached 35.9% (w/v), achieving yield of 467 g fructose from 675 g inulin containing chicory flour powder (0.69 g/g). LA received in course of the batch fermentation and fructose gained by the fed-batch are the highest amounts ever obtained from inulin, thus disclosing the key role of Mn2+ as a powerful tool to guide inulin conversion to targeted bio-chemicals.