Fermentation of Plant-Based Feeds with Lactobacillus acidophilus Improves the Survival and Intestinal Health of Juvenile Nile Tilapia (Oreochromis niloticus) Reared in a Biofloc System.

This study evaluated the effect of fermentation with Lactobacillus acidophilus on the biochemical and nutritional compositions of a plant-based diet and its effects on the productive performance and intestinal health of juvenile Nile tilapia (Oreochromis niloticus) reared in a biofloc technology (BFT) system. The in vitro kinetics of feed fermentation were studied to determine the L. acidophilus growth and acidification curve through counting the colony-forming units (CFUs) mL-1 and measuring the pH. Physicochemical and bromatological analyses of the feed were also performed. Based on the microbial growth kinetics results, vegetable-based Nile tilapia feeds fermented for 6 (FPB6) and 18 (FPB18) h were evaluated for 60 days. Fermented diets were compared with a positive control diet containing fishmeal (CFM) and a negative control diet without animal protein (CPB). Fermentation with L. acidophilus increased lactic acid bacteria (LAB) count and the soluble protein concentration of the plant-based feed, as well as decreasing the pH (p < 0.05). FPB treatments improved fish survival compared with CPB (p < 0.05). Fermentation increased feed intake but worsened feed efficiency (p < 0.05). The use of fermented feeds increased the LAB count and reduced pathogenic bacteria both in the BFT system's water and in the animals' intestines (p < 0.05). Fermented plant-based feeds showed greater villi (FPB6; FPB18) and higher goblet cell (FPB6) counts relative to the non-fermented plant-based feed, which may indicate improved intestinal health. The results obtained in this study are promising and show the sustainable potential of using fermented plant-based feeds in fish feeding rather than animal protein and, in particular, fishmeal.

Use of tannin-based coagulant and chlorine dioxide in treating brewing water: reduction of trihalomethanes and impact on physicochemical and sensory quality.

This study aimed to evaluate an alternative to reduce trihalomethane (THM) formation in brewing water. THM affects the organoleptic properties of water and, consequently, the produced beer. Water treatment based on common chemicals such as alum and free chlorine could potentially form THM. Therefore, we studied the replacement of chemicals used in water treatment: aluminum sulfate by a tannin-based coagulant and sodium hypochlorite by chlorine dioxide. Experimentally, jar tests were conducted, and the role of coagulants and oxidizing agents was evaluated for: the removal of apparent color, turbidity, natural organic matter (NOM) and microorganisms; the formation of trihalomethanes (THM); and the sensory quality of the water. Using tannin-based coagulant with chlorine dioxide was associated with the lowest THM in treated water (1.7 µg/L) and higher satisfaction in the sensory analysis. However, using these chemicals make the water treatment more expensive than the current strategy. Overall, using the tannin-based coagulant and chlorine dioxide treatment is an alternative to produce water with a lower THM concentration, better physical-chemical, and sensory quality. These findings motivate further brewing experiments and a deeper economics evaluation considering the process's sustainability.

Fermentation of Soybean Meal with Lactobacillus acidophilus Allows Greater Inclusion of Vegetable Protein in the Diet and Can Reduce Vibrionacea in the Intestine of the South American Catfish (Rhamdia quelen).

The objective of this study was to evaluate the effect of diets containing different inclusion levels (0%, 7%, 14%, 21% and 28%) of soybean meal fermented by Lactobacillus acidophilus (SMFL) on the zootechnical performance and intestinal health of South American catfish juveniles (Rhamdia quelen). The experimental design was completely randomized with five treatments and four replications and lasted 56 days. Five isoproteic (39% crude protein) and isoenergetic (4300 kcal of gross energy kg-1) diets were formulated where SMFL was included in replacement of fish meal. Two hundred forty South American catfish juveniles (3.0 ± 0.5 g) were distributed in 20 tanks (70 L) connected in a recirculation aquaculture system. At the end of the experiment, the inclusion of SMFL up to 21% in replacement of fish meal did not affect the zootechnical performance and also decreased the concentration of Vibrionaceae bacteria present in the intestine compared to the control group. The amount of total lactic and heterotrophic bacteria, the enzymatic activity and the intestinal morphometry did not differ between dietary treatments. The results demonstrate that fermentation with Lactobacillus acidophilus enables greater inclusion of soybean protein in South American catfish diets and promotes the control of intestinal pathogenic bacteria.

Application of a phosphonium-based ionic liquid for reactive textile dye removal: Extraction study and toxicological evaluation.

Textile dyeing processes are known for their negative environmental impacts due to the production of aqueous effluents containing toxic dyes. Therefore, new wastewater treatment processes need to be developed to treat such effluents, including Liquid-Liquid Extraction (LLE) process using Ionic Liquids (IL). This work aimed to evaluate the application of the hydrophobic IL trihexyltetradecylphosphonium decanoate to extract black, navy, and royal reactive dyes from water and evaluate the toxicological aspects of the resulting water stream. We investigated the effect of selected parameters, such as pH (2-12), temperature (20-50 °C), salt effects, dye concentration (0.5-50 mg/L), and phase volume ratio (900-9000) on the dye extraction. The results showed extraction yields as high as 97% for the three dyes and an extraction capacity of approximately 300 mg/g for black and navy dyes and 400 mg/g for royal. The toxicity tests involved Lactuca sativa, Triticum aestivium L, and Daphnia magna as bioindicators. The difference between the toxicity of the dye solutions before and after extraction was not statistically significant when L. sativa and Triticum aestivum L were used as bioindicators. However, the extracted solution showed increased toxicity towards D. magna due to traces of IL. Overall, the IL has a high extraction capacity for the black, navy, and royal dyes. Nevertheless, further studies on LLE associated with other processes must be carried out to reduce the risk linked to the toxicity of IL transferred to the water.

Immobilisation of phosphonium-based ionic liquid in polysulfone capsules for the removal of phenolic compounds, with an emphasis on 2,4-dichlorophenol, in aqueous solution.

Phosphonium-based ionic liquid immobilised in polysulfone capsules were prepared by the phase inversion technique for the adsorption of different phenolic compounds from aqueous solution. Some techniques, including Scanning Electron Microscopy (SEM), surface analysis by Brunauer-Emmett-Teller (BET), Fourier Transform Infrared Spectroscopy (FT-IR) and Thermogravimetric Analysis (TGA), were used to characterize the capsule and indicated that trihexyltetradecylphosphonium decanoate (ionic liquid) was successfully immobilised in polysulfone, the immobilisation was determined to be 63.29%. Adsorption tests showed that the developed capsules have the potential to remove varied phenolic compounds. For compounds 2,4-dichlorophenol (2,4-DCP) the best removal was achieved between pH 3.0 and 9.0. Temperature variation (25-70 °C) and sodium chloride concentration (0-1000 mg⋅L-1) had no significant changes in adsorption, demonstrating the scope for using this adsorbent with real effluents. Adsorption kinetics demonstrated the mechanism occurs in second order, the Weber-Morris model delimited the intraparticle diffusion as the adsorption limiter. The Redlich-Peterson model was the isothermal analysis that best suited the experimental data, with a ß value equal to 0.821 approaching the Langmuir model, which obtained a qmax of 404.50 mg⋅g-1. Consequently, these results demonstrate that these capsules have potential application in the treatment of environmental pollution caused by phenolic compounds.

Enhanced removal of phenol from biorefinery wastewater treatment using enzymatic and Fenton process.

The valorisation of biomass has been commonly carried out in biorefineries. The environmental concerns about these processes have not been intensely considered, demanding further investigations. Particularly, phenols are founded in high concentrations in biorefinery wastewater and are considered compounds of major concern. In this study, we evaluated the bioconversion of phenols by enzymatic treatment using the enzyme Horseradish peroxidase (HRP) and the Fenton process. The results showed an enzymatic phenol conversion of 97.5% at pH 7.0, enzyme activity of 0.8 U/mL and hydrogen peroxide concentration of 1.61 g/L. So as to enhance the treatment, we evaluate the Fenton reaction as a complementary process for further remaining phenol conversion. The best conditions for Fenton process were achieved using a hydrogen peroxide concentration and [H2O2]:[Fe] ratio of 3.90 g/L and 74, respectively, and the obtained phenol concentration in the treated wastewater was 0.11 mg/L. Chromatography analysis showed that 2-methoxyphenol was the majority compound in the original wastewater, which was subsequently precipitated by the enzymatic treatment. Furthermore, many physicochemical parameters were modified due to the treatment, such as biochemical oxygen demand, chemical oxygen demand and total organic carbon, with removal efficiencies of around 97, 49 and 46%, respectively. HRP combined with Fenton can be considered as an alternative methodology for the biorefinery wastewater treatment, especially regarding the phenols conversion.

Application of glycerol as carbon source for continuous drinking water denitrification using microorganism from natural biomass.

The contamination of water resources by nitrate is a global problem. Indeed, traditional treatment technologies are not able to remove this ion from water. Alternatively, biological denitrification is a useful technique for natural water nitrate removal. This study aimed to evaluate the use of glycerol as a carbon source for drinking water nitrate removal via denitrification in a reactor using microorganisms from natural biomass. The experiment was carried out in a continuous fixed bed reactor using immobilised microorganisms from the vegetal Phyllostachys aurea. The tests were started in batch mode to provide cells growth and further immobilisation on the support. Then, the treatment experiments were accomplished in an up-flow continuous reactor. Ethanol was used as the primary carbon source, and it was gradually replaced by glycerol. The C:N (carbon to nitrogen) ratio and the hydraulic residence time (HRT) were evaluated. It was possible to remove 98.14% of nitrate using a C:N ratio and HRT of 3:1 and 1.51 days, respectively. The results have demonstrated that glycerol is a potential carbon source for denitrification in a continuous reactor using immobilised cells from natural biomass.

Using natural biomass microorganisms for drinking water denitrification.

Among the methods that are studied to eliminate nitrate from drinking water, biological denitrification is an attractive strategy. Although several studies report the use of denitrifying bacteria for nitrate removal, they usually involve the use of sewage sludge as biomass to obtain the microbiota. In the present study, denitrifying bacteria was isolated from bamboo, and variable parameters were controlled focusing on optimal bacterial performance followed by physicochemical analysis of water adequacy. In this way, bamboo was used as a source of denitrifying microorganisms, using either Immobilized Microorganisms (IM) or Suspended Microorganisms (SM) for nitrate removal. Denitrification parameters optimization was carried out by analysis of denitrification at different pH values, temperature, nitrate concentrations, carbon sources as well as different C/N ratios. In addition, operational stability and denitrification kinetics were evaluated. Microorganisms present in the biomass responsible for denitrification were identified as Proteus mirabilis. The denitrified water was submitted to physicochemical treatment such as coagulation and flocculation to adjust to the parameters of color and turbidity to drinking water standards. Denitrification using IM occurred with 73% efficiency in the absence of an external carbon source. The use of SM provided superior denitrification efficiency using ethanol (96.46%), glucose (98.58%) or glycerol (98.5%) as carbon source. The evaluation of the operational stability allowed 12 cycles of biomass reuse using the IM and 9 cycles using the SM. After physical-chemical treatment, only SM denitrified water remained within drinking water standards parameters of color and turbidity.

Improved enzymatic performance of graphene-immobilized ß-glucosidase A in the presence of glucose-6-phosphate.

Optimization of cellulose enzymatic hydrolysis is crucial for cost-effective bioethanol production from lignocellulosic biomass. Enzyme immobilization in solid support allows enzyme recycling for reuse, lowering hydrolysis costs. Graphene is a nanomaterial isolated in 2004, which possesses exceptional properties for biomolecule immobilization. This study evaluates the potential for ß-glucosidase recycling by immobilization on graphene nanosheets. Data reported here demonstrated that graphene-immobilized ß-glucosidase can be recycled for at least eight cycles. Immobilization did not change the optimal temperature of catalysis and improved enzymatic stability upon storage. The role of glucose-6-phosphate on immobilized enzyme was also investigated, demonstrating that glucose-6-phosphate acts as a mixed-type activator and improves storage stability of immobilized enzyme. Complete cellulose hydrolysis using graphene-immobilized ß-glucosidase in the presence of glucose-6-phosphate resulted in greatly improved hydrolysis rates, demonstrating the potential of this strategy for biomass hydrolysis.

Immobilization of laccase from Aspergillus oryzae on graphene nanosheets.

Laccase enzymes of Aspergillus oryzae were immobilized on graphene nanosheets by physical adsorption and covalent bonding. Morphological features of the graphene sheets were characterized via microscopy techniques. The immobilization by adsorption was carried out through contact between graphene and solution of laccase enzyme dissolved in deionized water. The adsorption process followed a Freundlich model, showing no tendency to saturation within the range of values used. The process of immobilization by covalent bonding was carried out by nitration of graphene, followed by reduction of sodium borohydride and crosslinking with glutaraldehyde. The process of immobilization by both techniques increased the pH range of activity of the laccase enzyme compared to the free enzyme and increased its operating temperature. On operational stability, the enzyme quickly loses its activity after the second reaction cycle when immobilized via physical adsorption, while the technique by covalent bonding retained around 80% activity after six cycles.

Beta glucosidase from Bacillus polymyxa is activated by glucose-6-phosphate.

Optimization of cellulose enzymatic hydrolysis is crucial for cost effective bioethanol production from lignocellulosic biomass. Enzymes involved in cellulose hydrolysis are often inhibited by their end-products, cellobiose and glucose. Efforts have been made to produce more efficient enzyme variants that are highly tolerant to product accumulation; however, further improvements are still necessary. Based on an alternative approach we initially investigated whether recently formed glucose could be phosphorylated into glucose-6-phosphate to circumvent glucose accumulation and avoid inhibition of beta-glucosidase from Bacillus polymyxa (BGLA). The kinetic properties and structural analysis of BGLA in the presence of glucose-6-phosphate (G6P) were investigated. Kinetic studies demonstrated that enzyme was not inhibited by G6P. In contrast, the presence of G6P activated the enzyme, prevented beta glucosidase feedback inhibition by glucose accumulation and improved protein stability. G6P binding was investigated by fluorescence quenching experiments and the respective association constant indicated high affinity binding of G6P to BGLA. Data reported here are of great impact for future design strategies for second-generation bioethanol production.

Substrate specificity and enzyme recycling using chitosan immobilized laccase.

The immobilization of laccase (Aspergillus sp.) on chitosan by cross-linking and its application in bioconversion of phenolic compounds in batch reactors were studied. Investigation was performed using laccase immobilized via chemical cross-linking due to the higher enzymatic operational stability of this method as compared to immobilization via physical adsorption. To assess the influence of different substrate functional groups on the enzyme's catalytic efficiency, substrate specificity was investigated using chitosan-immobilized laccase and eighteen different phenol derivatives. It was observed that 4-nitrophenol was not oxidized, while 2,5-xylenol, 2,6-xylenol, 2,3,5-trimethylphenol, syringaldazine, 2,6-dimetoxyphenol and ethylphenol showed reaction yields up 90% at 40 °C. The kinetic of process, enzyme recyclability and operational stability were studied. In batch reactors, it was not possible to reuse the enzyme when it was applied to syringaldazne bioconversion. However, when the enzyme was applied to bioconversion of 2,6-DMP, the activity was stable for eight reaction batches.