Water quality is under constant threat worldwide due to the discharge of heavy metals into the water from industrial waste. In this report, we introduce a potential candidate, chitosan, extracted and isolated from shrimp shells, that can adsorb heavy metals from polluted water. The waste shrimp shell chitosan was characterized via Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The adsorption capacity of heavy metals on the modified shrimp shell was measured using an inductively coupled plasma mass spectrometry before and after adsorption. The highest adsorption of arsenic, nickel, and cobalt was 98.50, 74.50, and 47.82%, respectively, at neutral pH, whereas the highest adsorption of chromium was 97.40% at pH 3. Correspondingly, the maximum adsorption capacities of MSS for As, Cr, Ni, and Co were observed to be 15.92, 20.37, 7.00, and 6.27 mg/g, respectively. The application of Langmuir and Freundlich isotherm models revealed that the adsorption processes for the heavy metals were statistically significant (r² > 0.98). The kinetic studies of metal adsorption, using modified shrimp shell, were well explained by the pseudo-second-order kinetic model with linear coefficients (r²) of >0.97. The presence of a greater number of functional groups on the adsorbent, such as N–H coupled with H–O, –COO⁻, C–H, N–N, and C–O–C, was confirmed by FTIR analyses. Furthermore, SEM-EDX analysis detected the presence of elements on the surface of modified shrimp shell chitosan. This noteworthy adsorption capacity suggests that MSS could serve as a promising, eco-friendly, and low-cost adsorbent for removing toxic heavy metals including Cr, Ni, As, and Co and can be used in many broad-scale applications to clean wastewater.

This work was conducted to evaluate the effect of dilute sodium hydroxide (NaOH) on barley straw at boiling temperature and fractionation of its biomass components into lignin, hemicellulose, and reducing sugars. To this end, various concentrations of NaOH (0.5% to 2%) were applied for pretreatment of barley straw at 105 degrees C for 10 min. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy studies revealed that 2% NaOHpretreated barley straw exposed cellulose fibers on which surface granules were abolished due to comprehensive removal of lignin and hemicellulose. The X-ray diffractometer (XRD) result showed that the crystalline index was increased with increased concentration of NaOH and found a maximum 71.5% for 2% NaOH-pretreated sample. The maximum removal of lignin and hemicellulose was 84.8% and 79.5% from 2% NaOH-pretreated liquor, respectively. Reducing sugar yield was 86.5% from 2% NaOH-pretreated sample using an enzyme dose containing 20 FPU of cellulase, 40 IU of beta-glucosidase, and 4 FXU of xylanase/g substrate. The results of this study suggest that it is possible to produce the bioethanol precursor from barley straw using 2% NaOH at boiling temperature.

Application of greener pretreatment technology using robust ligninolytic bacteria for short duration to deconstruct rice straw and enhance bioethanol production is currently lacking. The objective of this study is to characterize three bacterial strains isolated from the milieux of cow rumen and forest soil and explore their capabilities of breaking down lignocellulose - an essential process in bioethanol production. Using biochemical and genomic analyses these strains were identified as Bacillus sp. HSTU-bmb18, Bacillus sp. HSTU-bmb19, and Citrobacter sp. HSTU-bmb20. Genomic analysis of the strains unveiled validated model hemicellulases, multicopper oxidases, and pectate lyases. These enzymes exhibited interactions with distinct lignocellulose substrates, further affirmed by their stability in molecular dynamic simulations. A comprehensive expression of ligninolytic pathways, including β-ketoadipate, phenyl acetate, and benzoate, was observed within the HSTU-bmb20 genome. The strains secreted approximately 75-82 U/mL of cellulase, xylase, pectinase, and lignin peroxidase. FT-IR analysis of the bacterial treated rice straw fibers revealed that the intensity of lignin-related peaks decreased, while cellulose-related peaks sharpened. The values of crystallinity index for the untreated control and the treated rice straw with either HSTU-bmb18, or HSTU-bmb19, or HSTU-bmb20 were recorded to be 34.48, 28.49, 29.36, 31.75, respectively, which are much higher than that of 13.53 noted for those treated with the bacterial consortium. The ratio of fermentable cellulose in rice straw increased by 1.25-, 1.79-, 1.93- and 2.17-fold following treatments with HSTU-bmb18, HSTU-bmb20, HSTU-bmb19, and a mixed consortium of these three strains, respectively. These aggregative results suggested a novel model for rice straw deconstruction utilizing hydrolytic enzymes of the consortium, revealing superior efficacy compared to individual strains, and advancing cost-effective, affordable, and sustainable green technology.