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This study aimed to isolate a novel archaeon capable of simultaneously producing methane and bioflocculants. The isolated methanogen was identified as Methanosarcina spelaei RK-23 by molecular characterization. Strain RK-23 grew with different carbon sources, but acetate was found to be the most beneficial carbon source for the production of methane and bioflocculants. Moreover, RK-23 produced methane and bioflocculants within an initial pH range of 5.0–8.0, with an optimal pH for methane production of 6.5 and flocculating activity of 7.0. In addition, strain RK-23 exhibited tolerance to high-salinity conditions and produced methane and bioflocculants within 0–1.2 M NaCl, with an optimum NaCl concentration of 0.3 M. The methane production and flocculating activity of strain RK-23 under optimal culture conditions were 17.4 mmol methane/mol acetate and 95.6%, respectively. MBF-23 mostly consisted of 83.5% carbohydrates and 14.3% proteins. Furthermore, the bridging of adsorption is believed to be the main bioflocculation mechanism in this study. • A novel bioflocculant-producing methanogen, Methanosarcina spelaei RK-23, was isolated. • RK-23 converted acetate to methane and MBF-23. • RK-23 secreted methane and MBF-23 within a wide salinity range. • MBF-23 was negatively charged, with a molecular weight of 3.5 × 106 Da. [ABSTRACT FROM AUTHOR]

A novel bioflocculant (MBF-79) prepared using formaldehyde wastewater as carbon resource was investigated in the study. The optimal conditions for bioflocculant production were determined to be an inoculum size of 7.0%, initial pH of 6.0, and formaldehyde concentration of 350 mg/L. An MBF-79 of 8.97 g/L was achieved as the maximum yield. Three main elements, namely C, H, and O, were present in MBF-79 with relative weigh percentages of 39.17%, 6.74%, and 34.55%, respectively. The Gel permeation chromatography analysis indicated that the approximate molecular weight (MW) of MBF-79 was 230 kDa. MBF-79 primarily comprised polysaccharide (71.2%) and protein (27.9%). Additionally, conditions for the removal of arsenic by MBF-79 were found to be MBF-79 at 120 mg/L, an initial pH 7.0, and a contact time 60 min. Under the optimal conditions, the removal efficiencies of arsenate (0.5 mg/L) and arsenite (0.5 mg/L) were 98.9% and 84.6%, respectively. Overall, these findings indicate bioflocculation offers an effective alternative method of decreasing arsenic during water treatment. [ABSTRACT FROM AUTHOR]

Highlights: [•] The bioflocculant-producing bacteria isolated from a sputum sample. [•] The bioflocculant is stable at wide ranges of pH and temperature. [•] Cation-independent bioflocculant produced by Klebsiella pneumoniae. [•] It could flocculate a variety of real wastewaters. [•] 79.4% flocculating activity for amoebae cysts was achieved with the bioflocculant. [ABSTRACT FROM AUTHOR]

High cost is one of the limiting factors in the industrial production of bioflocculant. Simultaneous preparation of bioflocculant from the contaminants in wastewater was considered as a potential approach to reduce the production cost. In this study, caprolactam was verified as sole feedstock for the growth of strain Alcaligenes faecalis subsp. phenolicus ZY-16 in batch experiments. Chemical analysis showed that the as-prepared MBF-16 consisted of heteropolysaccharides (88.3%) and peptides (9.4%). XPS result indicated the plentiful acylamino, hydroxyl and amino groups in MBF-16, which have an indispensable role in amoxicillin flocculation. The flocculation of amoxicillin can be well stimulated by Freundlich isotherm equation, and the K f was up to 178.6524 for amoxicillin. The kinetic fitting results proved that the flocculation of amoxicillin by MBF-16 was chemisorbed. This contribution may develop a novel technology for the preparation of bacterial flocculants that can consume toxic substrates (caprolactam) and have potential applications in amoxicillin removal. • Caprolactam could be an available feedstock to produce bioflocculants. • Hydroxyl, amino and acylamino groups are abundant in the bioflocculant. • Cation-independent flocculant is produced by Alcaligenes faecalis. • Chemisorption is involved in amoxicillin and the bioflocculant. [ABSTRACT FROM AUTHOR]