Background: Water pollution has become a major environmental and health concern due to increasing population and industrialisation. Microbial flocculants are promising agents for treatment of contaminated water owing to their effectiveness, eco-friendliness, and high biosafety levels. In this study, culture conditions of Providencia huaxiensis OR794369.1 were optimised and its bioflocculant was extracted, characterised and used to treat wastewater. Results: The maximum flocculating activity of 92% and yield of 3.5 g/L were obtained when cultivation conditions were: 3% inoculum size, starch, casein, initial pH of 6, cultivation temperature of 30 ^oC and 72 h of fermentation. The bioflocculant is an amorphous glycoprotein biomolecule with 37.5% carbohydrates, 27.9% protein, and 34.6% uronic acids. It is composed of hydroxyl, amino, alkanes, carboxylic acid and amines groups as its main functional structures. It was found to be safe to use as it demonstrated non-cytotoxic effects on bovine dermis and African green monkey kidney cells, illustrating median inhibitory concentration (IC₅₀) values of 180 and > 500 µg/mL on both cell lines, respectively. It demonstrated the removal efficiencies of 90% on chemical oxygen demand (COD), 97% on biological oxygen demand (BOD) and 72% on Sulphur on coal mine wastewater. It also revealed the reduction efficacies of 98% (COD) and 92% (BOD) and 70% on Sulphur on domestic wastewater. Conclusion: The bioflocculant was effective in reducing pollutants and thus, illustrated potential to be used in wastewater treatment process as an alternative.

Aloe arborescens Mill’s extracts have been explored for antibacterial and antioxidant efficacies. However, there is limited information on its chemical composition and mechanism of action. The purpose of this study was to assess the chemical composition, antibacterial and antioxidant activities and mechanism of the whole leaf extract of A. arborescens Mill. The phytochemical profile was analysed with gas chromatography mass spectrometry (GC-MS). The antioxidant and antibacterial activities were screened using 1,1diphenyl2picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and micro-dilution assays, respectively. The effects of the extract on the bacterial respiratory chain dehydrogenase, membrane integrity and permeability were analysed using iodonitrotetrazolium chloride, 260 absorbing materials and relative electrical conductivity assays. GC-MS spectrum revealed 26 compounds with N,N’-trimethyleneurea (10.56%), xanthine (8.57%) and 4-hexyl-1-(7-ethoxycarbonylheptyl)bicyclo[4.4.0]deca-2,5,7-triene (7.10%), being the major components. The extract also exhibited antioxidant activity with median concentration (IC₅₀) values of 0.65 mg/mL on DPPH and 0.052 mg/mL on ABTS. The extract exhibited minimum inhibitory concentration (MIC) values ranging from 0.07 to 1.13 mg/mL. The extract inhibited the bacterial growth by destructing the activity of the respiratory chain dehydrogenase, membrane integrity and permeability. Therefore, the leaf extract has the potential to serve as a source of antibacterial and antioxidant compounds.

The application of bioflocculants has become an alternative to that of chemical flocculants in wastewater treatment due to their environmental friendliness and non-toxic effects. This study aimed at isolating a bioflocculant-producing bacterium from marine water, optimisation of its culture conditions, and investigation of the removal efficiency of its bioflocculant on pollutants in wastewater. The bacterium was identified by 16S rRNA gene analysis. Optimal carbon and nitrogen sources, inoculum size, temperature, pH, and time were determined by the one-factor-at-a-time assay. The cytotoxicity of the bioflocculant was assessed on African green monkey kidney and bovine dermis cells using a tetrazolium-based columetric (MTT) method. Its removal efficiencies on chemical oxygen demand (COD), biological oxygen demand (BOD) and sulphur were determined using the Jar test method. The bacterial isolate was identified as Ochrobactrum oryzae AB84113. A maximum flocculating activity of 92% and a yield of 3.768 g/L were obtained when a 1% (v/v) inoculum size was used in the presence of starch and yeast extract at pH 7, 30 °C, and after 72 h of cultivation. The bioflocculant demonstrated non-cytotoxic effects on bovine dermis and African green monkey kidney cells. The bioflocculant removed 98% COD, 91% BOD and 86% of Sulphur. The bioflocculant has potential for pollutant removal from industrial wastewater.

Attention has been paid to bioflocculants production because of their effectiveness, innocuousness and environmental friendliness. This study aimed to characterise a bioflocculant from Bacillus megaterium BMBF and apply it in wastewater treatment. The proteins, carbohydrates and uronic acid were calculated using the Bradford, phenol–sulphuric acid and carbazole assays, respectively. An energy-dispersive X-ray (EDX) and infrared spectrometry were employed for the identification of the elemental composition and effective units, respectively. Cytotoxicity was carried out against Vero (African green monkey kidney) and bovine dermis cells using a colorimetric cytotoxicity assay. The reduction in chemical oxygen demand (COD) and biological oxygen demand (BOD) in domestic and coal mine wastewater was studied using the Jar test. The flocculant was composed of 12% protein, 27% carbohydrates and 61% uronic acid. Infrared spectrometry indicated hydroxyl, carboxyl and amino groups. EDX indicated C (61%) and O (17.5%) as the main elements. The bioflocculant revealed the mean inhibition concentration of 59 ug/mL against bovine dermis and 240 µg/mL on Vero cells. Maximum COD and BOD removal percentages of 97% and 99.3% were recorded on coal mine wastewater treatment and about 99.2% (COD) and 93% (BOD) on domestic wastewater. In conclusion, the bioflocculant from B. megaterium has potential industrial utility.

Bioflocculation has become the method of choice in wastewater treatment because of its effectiveness, environmental friendliness and innocuousness to humans. In this study, the bioflocculant-producing bacterium was isolated and its bioflocculant was used in wastewater treatment. The isolate was identified by 16S rRNA gene sequencing analysis. Its culture conditions (inoculum size, carbon and nitrogen sources, pH, temperature and time) were optimised using the one-factor-at-a-time assay. The cytotoxicity of the bioflocculant was assessed on human colorectal adenocarcinoma cells (Caco2) by tetrazolium-based colorimetric method. The ability of the bioflocculant to reduce biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in wastewater was evaluated using Jar test. The bacterium was identified as Bacillus subtilis CSM5 and the maximum flocculating activity of 92% was observed when fructose and urea were used as nutrients and the culture conditions were adjusted to 30 °C, pH 9, 160 rpm and 72 h of incubation. Caco2 exhibited 90% viability when the highest bioflocculant concentration of 200 µg/µL was used. The reduction of BOD and COD was achieved at 59 ± 3.1 and 75 ± 0.4%, respectively. In conclusion, B. subtilis CSM5 is a good candidate for bioflocculant production and its bioflocculant has good potential for use in wastewater treatment.

Heavy metal and microbial pollution in groundwater raises health concerns due to its adverse effects. This study aimed to assess the health risks associated with heavy metal and bacterial pollution in groundwater in Mankweng. Heavy metals and Escherichia coli were detected using inductively coupled plasma mass spectrophotometry and a Colilert system, respectively. The heavy metal pollution index (HPI) and non-carcinogenic and carcinogenic risks were computed. The β-Poisson dose–response model was employed to predict the probability of E. coli infection. The metals’ concentrations were all within the permissible limits of the South African National Standard (SANS). However, Pb levels at sites E and G exceeded the World Health Organization (WHO) guideline (≤0.01 mg/L). HPI values were all less than 100, indicative of low contamination. The hazard quotient values were all less than 1, except for vanadium. The cumulative cancer risk ranged between 3.06 × 10⁻⁵ and 1.81 × 10⁻⁴ and between 3.55 × 10⁻⁵ and 2.20 × 10⁻⁴ for adults and children, respectively. E. coli was only detected at site L. The annual risk of E. coli infection exceeded the WHO risk limit of 10⁻⁴. The results underscore the need for the regular monitoring of groundwater.