Use of Corn-Steep Water Effluent as a Promising Substrate for Lactic Acid Production by Enterococcus faecium Strain WH51-1

Synergistic approach for enhanced production of polyhydroxybutyrate by Bacillus pseudomycoides SAS-B1: Effective utilization of glycerol and acrylic acid through fed-batch fermentation and its environmental impact assessment

The continual rise in the consumption of petroleum-based synthetic polymers raised a significant environmental concern. Bacillus pseudomycoides SAS-B1 is a gram-positive rod-shaped halophilic bacterium capable of accumulating Polyhydroxybutyrate (PHB)-an intracellular biodegradable polymer. In the present study, the optimal conditions for cell cultivation in the seed media were developed. The optimal factors included a preservation age of 14 to 21 days (with 105 to 106 cells/mL), inoculum size of 0.1 % (w/v), 1 % (w/v) glucose, and growth temperature of 30 °C. The cells were then cultivated in a two-stage fermentation process utilizing glycerol and Corn Steep Liquor (CSL) as carbon and nitrogen sources, respectively. PHB yield was effectively increased from 2.01 to 9.21 g/L through intermittent feeding of glycerol and CSL, along with acrylic acid. FTIR, TGA, DSC, and XRD characterization studies were employed to enumerate the recovered PHB and determine its physicochemical properties. Additionally, the study assessed the cradle-to-gate Life Cycle Assessment (LCA) of PHB production, considering net CO2 generation and covering all major environmental impact categories. The production of 1000 kg of PHB resulted in lower stratospheric ozone depletion and comparatively reduced carbon dioxide emissions (2022.7 kg CO2 eq.) and terrestrial ecotoxicity (9.54 kg 1,4-DCB eq.) than typical petrochemical polymers.

Synthesis, Optimization, and Characterization of Cellulase Enzyme Obtained from Thermotolerant Bacillus subtilis F3: An Insight into Cotton Fabric Polishing Activity

The efficacy of 40 bacterial isolates obtained from hot spring water samples to produce cellulase enzymes was investigated. As a result, the strain Bacillus subtilis F3, which was identified using traditional and molecular methods, was selected as the most potent for cellulase production. Optimization was carried out using one-factor-at-a-time (OFAT) and BOX-Behnken Design to detect the best conditions for the highest cellulase activity. This was accomplished after an incubation period of 24 h at 45°C and pH 8, with an inoculum size of 1% (v/v), 5 g/l of peptone as nitrogen source, and 7.5 g/l of CMC. Moreover, the best concentration of ammonium sulfate for cellulase enzyme precipitation was 60% followed by purification using a dialysis bag and Sephadex G-100 column chromatography to collect the purified enzyme. The purified cellulase enzyme was characterized by 5.39-fold enrichment, with a specific activity of 54.20 U/mg and a molecular weight of 439 kDa. There were 15 amino acids involved in the purified cellulase, with high concentrations of 160 and 100 mg/l for glycine and proline respectively. The highest stability and activity of the purified cellulase was attained at pH 7 and 50°C in the presence of 150 ppm of CaCl2, NaCl, and ZnO metal ions. Finally, the biopolishing activity of the cellulase enzyme, as indicated by weight loss percentages of the cotton fabric, was dependent on concentration and treatment time. Overall, the thermotolerant B. subtilis F3 strain has the potential to provide highly stable and highly active cellulase enzyme for use in biopolishing of cotton fabrics.

Saccharina latissima, candy-factory waste, and digestate from full-scale biogas plant as alternative carbohydrate and nutrient sources for lactic acid production

To substitute petroleum-based materials with bio-based alternatives, microbial fermentation combined with inexpensive biomass is suggested. In this study Saccharina latissima hydrolysate, candy-factory waste, and digestate from full-scale biogas plant were explored as substrates for lactic acid production. The lactic acid bacteria Enterococcus faecium, Lactobacillus plantarum, and Pediococcus pentosaceus were tested as starter cultures. Sugars released from seaweed hydrolysate and candy-waste were successfully utilized by the studied bacterial strains. Additionally, seaweed hydrolysate and digestate served as nutrient supplements supporting microbial fermentation. According to the highest achieved relative lactic acid production, a scaled-up co-fermentation of candy-waste and digestate was performed. Lactic acid reached a concentration of 65.65 g/L, with 61.69% relative lactic acid production, and 1.37 g/L/hour productivity. The findings indicate that lactic acid can be successfully produced from low-cost industrial residues.

Adaptive laboratory evolution to hypersaline conditions of lactic acid bacteria isolated from seaweed

Seaweed biomass has been proposed as a promising alternative carbon source for fermentation processes using microbial factories. However, the high salinity content of seaweed biomass is a limiting factor in large scale fermentation processes. To address this shortcoming, three bacterial species (Pediococcus pentosaceus, Lactobacillus plantarum, and Enterococcus faecium) were isolated from seaweed biomass and evolved to increasing concentrations of NaCl. Following the evolution period, P. pentosaceus reached a plateau at the initial NaCl concentration, whereas L. plantarum, and E. faecium showed a 1.29 and 1.75-fold increase in their salt tolerance, respectively. The impact that salt evolution had on lactic acid production using hypersaline seaweed hydrolysate was investigated. Salinity evolved L. plantarum produced 1.18-fold more lactic acid than the wild type, and salinity evolved E. faecium was able to produce lactic acid, while the wild type could not. No differences in lactic acid production were observed between the P. pentosaceus salinity evolved and wild type strains. Evolved lineages were analyzed for the molecular mechanisms underlying the observed phenotypes. Mutations were observed in genes affecting the ion balance in the cell, the composition of the cell membrane and proteins acting as regulators. This study demonstrates that bacterial isolates from saline niches are promising microbial factories for the fermentation of saline substrates, without the requirement of previous desalination steps, while preserving high final product yields.

Microbial production of lactic acid using organic wastes as low-cost substrates

Lactic acid is a natural organic acid with diverse of applications in food, pharmaceutical, cosmetics, and chemical industry. Recently, the demand of lactic acid has been grown due to its utilization for polylactic acid production. Microbial production of lactic acid production is preferable due to optical purity of product, utilization of low cost substrates, and low energy requirement. Lignocellulosic biomass and other organic wastes are considered potential raw materials for cost-effective production of lactic acid. The raw materials are either hydrolyzed by enzymes or dilute acids to release the reducing sugars that are fermented in to lactic acid. This review has been focussed on microbial production of lactic acid using different organic wastes as low cost substrate.

Development and Utilization of Corn Processing by-Products: A Review

As an important food crop, corn has an important impact on people's lives. The processing of corn produces many by-products, such as corn gluten meal, corn husk, and corn steep liquor, which are rich in protein, oil, carbohydrates, and other nutrients, all of which are inexpensive. Their accumulation in large quantities during the production process not only results in a burden on the environment but also the loss of potentially valuable food materials that can be processed. In fact, the by-products of corn processing have been partially used in functional foods, nutrients, feed, and other industries. There is no doubt that the secondary utilization of these by-products can not only solve the problem of waste pollution caused by them, but also produce high value-added products and improve the economic benefits of corn. This paper describes in detail the processing and higher-value utilization of the five main by-products: corn gluten meal, corn husks, corn steep liquor, corn germ, and fuel ethanol by-product. The utilization status of corn processing by-products was discussed roundly, and the development trend of corn processing by-products in China and other countries was analyzed, which provided the reference for the development of the corn deep processing industry.

Enterococcus faecium s6 Enabled Efficient Homofermentative Lactic Acid Production from Xylan-Derived Sugars

A thermotolerant Enterococcus faecium s6 strain exhibited homoferementative lactic acid (LA) production at high xylose concentration (≥50 g/L). In batch fermentation at 45 °C and controlled pH of 6.5, strain E. faecium s6 produced up to 72.9 g/L of LA with a yield of 0.99 g/g-consumed xylose and productivity of 1.74 g/L.h from 75 g/L xylose. An increased LA concentration and productivities with high yields were obtained in repeated batch fermentation that was conducted for 24 runs. In this mode, the strain could produce LA up 81.1 g/L within 5 h fermentation at a high productivity of 13.5 g/L.h and a yield of 1.02 g/g-consumed xylose. The strain was unable to consume birchwood xylan as sole carbon source. However, it could efficiently utilize xylooligosaccharides of xylobiose, xylotriose, xylotetraose, xylopentaose, and xylohexaose. The intracellular xylosidase activity was induced by xylose. Using xylooligosaccharide (50 g/L)/xylose (5 g/L) mixtures, the strain was able to produce maximum LA at 48.2 g/L within 120 h at a yield of 1.0 g/g-consumed sugar and productivity of 0.331 g/L.h. These results indicate that E. faecium s6 is capable of directly utilizing xylan-hydrolyzate and will enable the development of a feasible and economical approach to the production of LA from hemicellulosic hydrolysate.

L-Lactate oxidase-mediated removal of L-lactic acid derived from fermentation medium for the production of optically pure D-lactic acid

BACKGROUND

There has been an increasing demand for optically pure D-lactic and L-lactic acid for the production of stereocomplex-type polylactic acid. The D-lactic acid production from lignocellulosic biomass is important owing to its great abundance in nature. Corn steep liquor (CSL) is a cheap nitrogen source used for industrial fermentation, though it contains a significant amount of L-lactic acid, which decreases the optical purity of D-lactic acid produced.

METHOD AND RESULTS

To remove L-lactic acid derived from the CSL-based medium, L-lactate oxidase (LoxL) from Enterococcus sp. NBRC 3427 was expressed in an engineered Lactiplantibacillus plantarum (formally called Lactobacillus plantarum) strain KOLP7, which exclusively produces D-lactic acid from both hexose and pentose sugars. When the resulting strain was applied for D-lactic acid fermentation from the mixed sugars consisting of the major constituent sugars of lignocellulose (35 g/L glucose, 10 g/L xylose, and 5 g/L arabinose) using the medium containing 10 g/L CSL, it completely removed L-lactic acid derived from CSL (0.52 g/L) and produced 41.7 g/L of D-lactic acid. The L-lactic acid concentration was below the detection limit, and improvement in the optical purity of D-lactic acid was observed (from 98.2% to > 99.99%) by the overexpression of LoxL.

CONCLUSION AND IMPLICATIONS

The LoxL-mediated consumption of L-lactic acid would enable the production of optically pure D-lactic acid in any medium contaminated by L-lactic acid. This article is protected by copyright. All rights reserved.

Contribution of Fermentation Technology to Building Blocks for Renewable Plastics

Large-scale worldwide production of plastics requires the use of large quantities of fossil fuels, leading to a negative impact on the environment. If the production of plastic continues to increase at the current rate, the industry will account for one fifth of global oil use by 2050. Bioplastics currently represent less than one percent of total plastic produced, but they are expected to increase in the coming years, due to rising demand. The usage of bioplastics would allow the dependence on fossil fuels to be reduced and could represent an opportunity to add some interesting functionalities to the materials. Moreover, the plastics derived from bio-based resources are more carbon-neutral and their manufacture generates a lower amount of greenhouse gasses. The substitution of conventional plastic with renewable plastic will therefore promote a more sustainable economy, society, and environment. Consequently, more and more studies have been focusing on the production of interesting bio-based building blocks for bioplastics. However, a coherent review of the contribution of fermentation technology to a more sustainable plastic production is yet to be carried out. Here, we present the recent advancement in bioplastic production and describe the possible integration of bio-based monomers as renewable precursors. Representative examples of both published and commercial fermentation processes are discussed.

Evaluate the Toxicity of Pyrethroid Insecticide Cypermethrin before and after Biodegradation by Lysinibacillus cresolivuorans Strain HIS7

Herein, bacterial isolate HIS7 was obtained from contaminated soil and exhibited high efficacy to degrade pyrethroid insecticide cypermethrin. The HIS7 isolate was identified as Lysinibacillus cresolivuorans based on its morphology and physiology characteristics as well as sequencing of 16S rRNA. The biodegradation percentages of 2500 ppm cypermethrin increased from 57.7% to 86.9% after optimizing the environmental factors at incubation condition (static), incubation period (8-days), temperature (35 °C), pH (7), inoculum volume (3%), and the addition of extra-carbon (glucose) and nitrogen source (NH₄Cl₂). In soil, L. cresolivuorans HIS7 exhibited a high potential to degrade cypermethrin, where the degradation percentage increased from 54.7 to 93.1% after 7 to 42 days, respectively. The qualitative analysis showed that the bacterial degradation of cypermethrin in the soil was time-dependent. The High-Performance Liquid Chromatography (HPLC) analysis of the soil extract showed one peak for control at retention time (R.T.) of 3.460 min and appeared three peaks after bacterial degradation at retention time (R.T.) of 2.510, 2.878, and 3.230 min. The Gas chromatography-mass spectrometry (GC-MS) analysis confirmed the successful degradation of cypermethrin by L. cresolivuorans in the soil. The toxicity of biodegraded products was assessed on the growth performance of Zea mays using seed germination and greenhouse experiment and in vitro cytotoxic effect against normal Vero cells. Data showed the toxicity of biodegraded products was noticeably decreased as compared with that of cypermethrin before degradation.