Bioflocculation of pollutants in wastewater using flocculant derived from Providencia huaxiensis OR794369.1.

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.

Antimicrobial, antioxidant and cytotoxic activities of the leaf and stem extracts of Carissa bispinosa used for dental health care.

BACKGROUND: Carissa bispinosa (L.) Desf. ex Brenan is one of the plants used traditionally to treat oral infections. However, there is limited data validating its therapeutic properties and photochemistry. The aim of this study was to investigate the protective efficacy of the leaf and stem extracts of C. bispinosa against oral infections. METHODS: The phenolic and tannin contents were measured using Folin-Ciocalteau method after extracting with different solvents. The minimum inhibitory concentrations (MIC) of the extracts were assessed using the microdilution method against fungal (Candida albicans and Candida glabrata) and bacterial (Streptococcus pyogenes, Staphylococcus aureus and Enterococcus faecalis) strains. The 2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing power (FRP) models were utilised to assess the antioxidant potential of the extracts. Cytotoxicity of the leaf acetone extract was evaluated using the methylthiazol tetrazolium assay. RESULTS: The methanol leaf extract had the highest phenolic content (113.20 mg TAE/g), whereas hexane extract displayed the highest tannin composition of 22.98 mg GAE/g. The acetone stem extract had the highest phenolic content (338 mg TAE/g) and the stem extract yielded the highest total tannin content (49.87 mg GAE/g). The methanol leaf extract demonstrated the lowest MIC value (0.31 mg/mL), whereas the stem ethanol extract had the least MIC value of 0.31 mg/mL. The stem methanol extract had the best DPPH free radical scavenging activity (IC50, 72 µg/mL) whereas the stem ethanol extract displayed maximum FRP with absorbance of 1.916. The leaf acetone extract had minimum cytotoxicity with the lethal concentration (LC50) of 0.63 mg/mL. CONCLUSIONS: The results obtained in this study validated the protective effect of C. bispinosa against oral infections.

Chemical Profile, Antioxidant and Antibacterial Activities, Mechanisms of Action of the Leaf Extract of Aloe arborescens Mill.

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.

Bioprospecting of endophytic actinobacterium associated with Aloe ferox mill for antibacterial activity.

BACKGROUND: The emergence of drug resistance among pathogens has resulted in renewed interest in bioprospecting for natural microbial products. METHODS: This study aimed to bioprospecting endophytic actinobacterium associated with Aloe ferox Mill for its antibacterial activity. Endophytic actinomycetes were isolated from the gel of A. ferox Mill by surface sterilization technique using actinomycete isolation agar. The isolate with a promising antibacterial activity was identified using 16S rRNA sequence analysis. The minimum inhibitory concentration (MIC) of the extract was assessed by the micro-dilution method and its effect on the respiratory chain dehydrogenase (RCD) activity was ascertained by the iodonitrotetrazolium chloride (INT) assay. Fourier transform-infrared spectrophotometer (FTIR) and gas chromatography-mass spectrophotometry (GC-MS) were employed to identify functional groups and the chemical constituents, respectively. RESULTS: The actinobacterium was found to be Streptomyces olivaceus CP016795.1. Its extract displayed noteworthy antibacterial activity (MIC ≤1 mg/mL) against Staphylococcus aureus (ATCC 25925), Bacillus cereus (ATCC 10102), and Escherichia coli (ATCC 25922); and showed an inhibitory effect on the RCD activity. FTIR spectrum displayed hydroxyl, amine, and aromatic groups, and the GC-MS revealed 5-Hydroxymethylfurfural as the main constituent (19.47%). CONCLUSIONS: S. olivaceus CP016795.1 can serve as a potential source of effective antibacterial compounds.

Isolation and Optimisation of Culture Conditions for a Marine Bioflocculant-Producing Bacterium and Application of Its Bioflocculant in Wastewater Treatment.

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.

Isolation of endophytic bacteria from the leaves of Anredera cordifolia CIX1 for metabolites and their biological activities.

BACKGROUND: Endophytes, especially those that are found from ethnopharmacologically noteworthy medicinal plants have attracted attention due to their diverse bioactive metabolites of pharmacological importance. METHODS: This study aimed at isolating endophytic bacterium from the leaves of Anredera cordifolia CIX1 for its bioactive metabolites. The endophytic isolates were identified by 16S rRNA sequence and investigated for antibiotic sensitivity using different antibiotics. The secondary metabolites were evaluated for antibacterial activity against four bacterial strains. The 2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2'-azinobis (3- ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods were used to assess their scavenging activities. The chemical components were analysed by gas chromatography-mass spectrometry (GC-MS). RESULTS: Out of 13 isolates, Isolate 1 was identified as Pseudomonas aeruginosa CP043328.1. It was resistant to clindamycin, ertapenem, penicillin G, amoxicillin, cephalothin and kanamycin but sensitive to imipenem, meropenem, and gentamycin. Its extract demonstrated antibacterial activity with minimum inhibitory concentration value of 0.098 against Bacillus cereus (ATCC 10102) and Staphylococcus aureus (ATCC 25925) and 0.391 mg/ml against Escherichia coli (ATCC 25922) and Proteus mirabilis (ATCC 25933). The extract revealed DPPH and ABTS scavenging activities with half maximal inhibitory concentration value of 0.650 mg/ml and 0.15 mg/ml, respectively. The GC-MS revealed a total of 15 compounds with diisooctyl phthalate (50.51%) and [1, 2, 4] oxadiazole, 5-benzyl-3 (10.44%) as major components. CONCLUSIONS: P. aeruginosa CP043328.1 produced secondary metabolites with antibacterial and antioxidant activities.

Removal of Pollutants in Mine Wastewater by a Non-Cytotoxic Polymeric Bioflocculant from Alcaligenes faecalis HCB2.

Bioflocculation is a physicochemical technique often employed to efficiently remove colloidal water pollutants. Consequently, in this study, a bioflocculant was produced, characterised and applied to remove pollutants in mine wastewater. The maximum flocculation activity of 92% was recorded at 30 °C, pH 9.0 when maltose and urea were used as energy sources and 72 h of fermentation at the inoculum size of 1% (v/v). K+ proved to be a favourable cation. The bioflocculant yield of 4 g/L was obtained. Scanning electron microscopy illustrated a hexagonal-like structure of the bioflocculant. It is composed of carbohydrates and proteins in mass proportion of 88.6 and 9.5%, respectively. The Fourier transform infrared spectrum revealed the presence of hydroxyl, amide and amino functional groups. More than 73% of the bioflocculant was obtained after exposure to 600 °C using the thermogravimetric analyser. Human embryonic kidney 293 (HEK 293) cells exhibited 95% viability after being treated with 200 µg/µL of the bioflocculant. The flocculation mechanisms were proposed to be as a result of a double layer compression by K+, chemical reactions and bridging mechanism. The removal efficiencies of 59, 72, and 75% on biological oxygen demand, chemical oxygen demand and sulphur, were obtained respectively. Thus, the bioflocculant have potential use in wastewater treatment.