Enhanced methylene blue decolourization by Rhodococcus strain UCC 0003 grown in banana peel agricultural waste through response surface methodology

Anionic dye removal by immobilized bacteria into alginate-polyvinyl alcohol-bentonite matrix

Methyl orange (MO) is commonly used in the textile dyeing industry, posing serious health and environmental hazards due to its carcinogenic, mutagenic properties, and potential for bioaccumulation. Appropriate handling is needed to solve these problems by harnessing the capacity of living microorganisms and the adsorption properties of bentonite clay minerals. Although the conventional approach predominantly depends on free cells, recent study has developed other methods such as immobilization techniques. Therefore, this study aimed to investigate the efficiency of the immobilization matrix comprising sodium alginate (SA), polyvinyl alcohol (PVA), and bentonite by modifying Pseudomonas aeruginosa, Bacillus subtilis, and Ralstonia pickettii for MO removal of 50 mg/L. In the free cell technique, the results showed that the MO decreased to 43.13, 36.61, and 27.45% for each of the bacteria within 10 days at 35 °C. The bacterial immobilization technique, including live immobilized P. aeruginosa (LIPa), live immobilized B. subtilis (LIBs), and live immobilized R. pickettii (LIRp) beads also demonstrated significant efficiency, achieving MO removal rates up to 97.15, 95.65, and 66.63% within 10 days. These synthesized beads showed reusability, with LIPa, LIBs, and LIRp being used up to 4, 4, and 2 cycles, respectively. The external and internal surface conditions were observed using SEM instrument and the results showed that all components were agglomerated. Comparisons using dead bacterial biomass indicated that treatment with live bacteria consistently yielded significantly higher removal rates. These results showed the effectiveness of immobilized bacteria in MO removal, offering a promising potential in reducing pollutants.

Modeling and optimization of biodegradation of methylene blue by Staphylococcus aureus through a statistical optimization process: a sustainable approach for waste management

Bacterial species for metabolizing dye molecules were isolated from textile wastewater. The best microbial species for such an application was selected amongst the isolated bacterial populations by conducting methylene blue (MB) batch degradation studies with the bacterial strains. The most suitable bacterial species was Staphylococcus aureus (S. aureus). Process parameters were optimized using Full Factorial Design (FFD) and under the optimum conditions (pH of 5, temperature of 35 °C, 150 ppm, and time of 8 h). Response Surface Methodology (RSM) modeling technique was applied to model the process and their performance and predictive capabilities of the response (removal efficiency) was also examined. When tested with 20 ppm dye using batch reactors, the maximum COD and color removal efficiencies, were found to be 88% and 98%, respectively. Our results showed that Staphylococcus aureus had a high decolorization capacity. UV-Visible and Fourier-transform infrared (FTIR) spectroscopy analysis confirmed the biodegradation of MB. Using phytotoxicity and mutagenicity endpoints, toxicological studies of MB before and after biodegradation were studied. Toxicity assay signaled that biodegradation led to the detoxification of MB dye.

Utilization of sugarcane straw for production of β-glucan biopolymer by Lasiodiplodia theobromae CCT 3966 in batch fermentation process

β-Glucans as emerging biopolymer are widely produced by microorganisms in fermentation processes using commercial sugars which make process non-economic. Lignocellulosic substances are inexpensive carbon sources, which could be exploited for sustainable production of β-glucans. In this study, a lignocellulosic material, namely sugarcane straw (SCS) was utilized for the production of extracellular β-glucan by Lasiodiplodia theobromae CCT3966. SCS was subjected to acid and subsequent alkaline pretreatment, followed by enzymatic saccharification using cellulase enzyme. Quantity of 48.65 g/L glucose was released after enzymatic hydrolysis. β-Glucan production was performed by cultivation of fungal strain in SCS hydrolysate at 28 °C and initial culture pH 7. Highest β-glucan yield and productivity of 0.047 gg^-1 and 0.014 gL^-1h^-1, respectively was obtained at 72 h fermentation time. Kinetic study of β-glucan production revealed experimental biosynthesis of β-glucan from SCS hydrolysate followed the trend generated by Logistic and Luedeking-Piret models. Chemical structure of biopolymer produced showed β-glucan constitution.