Performance of various cyanide degrading bacteria on the biodegradation of free cyanide in water

This study reports on the biodegradation of free cyanide (FCN) by cyanide degrading bacteria (CDB) that were isolated from mining wastewater and thiocyanate containing wastewater. The performance of these isolates was compared to cryopreserved CDBs that were used in previous studies. The performance of the isolates to degrade FCN was studied in batch cultures. It was observed that the CDB from the thiocyanate wastewater showed higher biodegradation rates (2.114 g CN^-. L^-1.O.D_600 nm^-1.h^-1) compared to the isolates from the mining wastewater. The isolates from the cryopreserved CDBs and from the mining wastewater achieved a biodegradation rate of 1.285 g CN^- L^-1.O.D_600 nm^-1.h^-1 and 1.209 g CN^-.L^-1.O.D_600 nm^-1.h^-1, respectively. This study demonstrated that the source of the organisms plays a significant role on FCN biodegradation.

Industrial textile effluent treatment and antibacterial effectiveness of Zea mays L. Dry husk mediated bio-synthesized copper oxide nanoparticles

Zea mays L. dry husk extract was used to bio synthesize copper oxide nanoparticles. Red coloured cubic Cu₂O nanoparticles were obtained for the first time via this simple, eco- friendly, green synthesis route. The Cu₂O nanoparticles were thermally oxidized to pure monoclinic CuO nanoparticles at 600 °C. The phases of the copper oxides were confirmed from the x-ray diffraction (XRD) studies. The nanoparticle sizes as obtained from high resolution transmission electron microscope (HRTEM) analysis range from 10 to 26 nm, 36-73 nm and 30-90 nm for the unannealed Cu₂O, 300 °C and 600 °C annealed CuO respectively. The values of the bandgap energies obtained from diffuse reflectance of the nanoparticles are 2.0, 1.30 and 1.42 eV respectively for the unannealed, 300 °C, and 600 °C annealed copper oxide nanoparticles. The 600 °C annealed copper oxide nanoparticles showed 91% and 90% degradation ability for methylene blue dye (BM) and textile effluent (TE) respectively under visible light irradiation. While CuO_300 is more effective to inhibit the growth of Escherichia coli 518,133 and Staphylococcus aureus 9144, Cu₂O is better for Pseudomonas aeruginosa and Bacillus licheniformis. The results confirm the photo-catalytic and anti-microbial effectiveness of the copper oxide nanoparticles.

Product and Microbial Population Kinetics During Balsamic-Styled Vinegar Production

Balsamic-styled vinegar is a nutraceutical product obtained from a two-stage fermentation process of grape must. However, little is known about how fermentation conditions affect growth kinetics, bio-product development, population dynamics and the final product quality. As a result, the current study investigated the effect of fermentation temperature and inoculation strategy on the fermentation dynamics of Balsamic-styled vinegar production. A microbial consortium of non-Saccharomyces yeasts (n = 13) and acetic acid bacteria (n = 5) was tested at various fermentation temperatures (22 °C, 28 °C and a fluctuating temperature regimen). Different inoculation strategies (co-inoculation and sequential inoculation) were investigated, and population dynamics of the product selected due to a rapid fermentation period were confirmed using a 16S and 18S gene sequencing. A higher fermentation temperature (28 °C) and co-inoculation strategy resulted in a shorter fermentation cycle, whilst the desired acetic acid concentration of 60 g/L was achieved within 38 days. 16S and 18S gene sequencing showed that 50.84% of Acetobacter species were abundant at the end of the fermentation cycle, while 40.18% bacteria were unculturable. The study provides a better understanding of how fermentation temperature and inoculation strategy affect the fermentation period, population dynamics and the growth kinetics of the microbial consortium during the production of Balsamic-styled vinegar. PRACTICAL APPLICATION: Lower quality South African wine grapes could be channelled to an alternative high-priced product (Balsamic-styled vinegar), with low technological input requirements. Thus, making it easier to incorporate a low capital start-up business while empowering small business entrepreneurs and boosting the economy.

A bioflocculant-supported dissolved air flotation system for the removal of suspended solids, lipids and protein matter from poultry slaughterhouse wastewater

In this study, two previously identified isolates, i.e. Comamonas aquatica (BF-3) and Bacillus sp. BF-2, were determined to be suitable candidates to utilise in a bioflocculant-supported dissolved air flotation (Bio-DAF) system as a pretreatment system for poultry slaughterhouse wastewater (PSW). A 2% (v/v) (bioflocculant:PSW) strategy was used for the DAF to reduce total suspended solids (TSS), lipids and proteins in the PSW, by supplementing the bioflocculants produced and the co-culture (C. aquatica BF-3 and Bacillus sp. BF-2) directly into the DAF. The Bio-DAF was able to reduce 91% TSS, 79% proteins and 93% lipids when the DAF system was operating at steady state, in comparison with a chemical DAF operated using 2% (v/v) alum that was able to only reduce 84% TSS, 71% proteins and 92% lipids. It was concluded that the Bio-DAF system worked efficiently for the removal of suspended solids, lipids and proteins, achieving better results than when alum was used.

Treatment of poultry slaughterhouse wastewater using a static granular bed reactor (SGBR) coupled with ultrafiltration (UF) membrane system

The South African poultry industry has grown exponentially in recent years due to an increased demand for their products. As a result, poultry plants consume large volumes of high quality water to ensure that hygienically safe poultry products are produced. Furthermore, poultry industries generate high strength wastewater, which can be treated successfully at low cost using anaerobic digesters. In this study, the performance of a bench-scale mesophilic static granular bed reactor (SGBR) containing fully anaerobic granules coupled with an ultrafiltration (UF) membrane system, as a post-treatment system, was investigated. The poultry slaughterhouse wastewater was characterized by a chemical oxygen demand (COD) range between 1,223 and 9,695mg/L, average biological oxygen demand of 2,375mg/L and average fats, oil and grease (FOG) of 554mg/L. The SGBR anaerobic reactor was operated for 9 weeks at different hydraulic retention times (HRTs), i.e. 55 and 40 h, with an average organic loading rate (OLR) of 1.01 and 3.14g COD/L.day. The SGBR results showed an average COD, total suspended solids (TSS) and FOG removal of 93%, 95% and 90% respectively, for both OLR. The UF post-treatment results showed an average of COD, TSS and FOG removal of 64%, 88% and 48%, respectively. The overall COD, TSS and FOG removal of the system (SGBR and UF membrane) was 98%, 99.8%, and 92.4%, respectively. The results of the combined SGBR reactor coupled with the UF membrane showed a potential to ensure environmentally friendly treatment of poultry slaughterhouse wastewater.

An integrated biological approach for treatment of cyanidation wastewater

The cyanidation process has been, and still remains, a profitable and highly efficient process for the recovery of precious metals from ores. However, this process has contributed to environmental deterioration and potable water reserve contamination due to the discharge of poorly treated, or untreated, cyanide containing wastewater. The process produces numerous cyanide complexes in addition to the gold cyanocomplex. Additionally, the discharge constituents also include hydrogen cyanide (HCN) - metallic complexes with iron, nickel, copper, zinc, cobalt and other metals; thiocyanate (SCN); and cyanate (CNO). The fate of these complexes in the environment dictates the degree to which these species pose a threat to living organisms. This paper reviews the impact that the cyanidation process has on the environment, the ecotoxicology of the cyanidation wastewater and the treatment methods that are currently utilised to treat cyanidation wastewater. Furthermore, this review proposes an integrated biological approach for the treatment of the cyanidation process wastewater using microbial consortia that is insensitive and able to degrade cyanide species, in all stages of the proposed process.

Isolation of high-salinity-tolerant bacterial strains, Enterobacter sp., Serratia sp., Yersinia sp., for nitrification and aerobic denitrification under cyanogenic conditions

Cyanides (CN(-)) and soluble salts could potentially inhibit biological processes in wastewater treatment plants (WWTPs), such as nitrification and denitrification. Cyanide in wastewater can alter metabolic functions of microbial populations in WWTPs, thus significantly inhibiting nitrifier and denitrifier metabolic processes, rendering the water treatment processes ineffective. In this study, bacterial isolates that are tolerant to high salinity conditions, which are capable of nitrification and aerobic denitrification under cyanogenic conditions, were isolated from a poultry slaughterhouse effluent. Three of the bacterial isolates were found to be able to oxidise NH(4)-N in the presence of 65.91 mg/L of free cyanide (CN(-)) under saline conditions, i.e. 4.5% (w/v) NaCl. The isolates I, H and G, were identified as Enterobacter sp., Yersinia sp. and Serratia sp., respectively. Results showed that 81% (I), 71% (G) and 75% (H) of 400 mg/L NH(4)-N was biodegraded (nitrification) within 72 h, with the rates of biodegradation being suitably described by first order reactions, with rate constants being: 4.19 h(-1) (I), 4.21 h(-1) (H) and 3.79 h(-1) (G), respectively, with correlation coefficients ranging between 0.82 and 0.89. Chemical oxygen demand (COD) removal rates were 38% (I), 42% (H) and 48% (G), over a period of 168 h with COD reduction being highest at near neutral pH.

Optimisation of bioflocculant production by a biofilm forming microorganism from poultry slaughterhouse wastewater for use in poultry wastewater treatment

Poultry slaughterhouse wastewater contains nutrients that are sufficient for microbial growth; moreover, the wastewater has microorganisms which can be harnessed to perform specific functions. Additionally, these microorganisms can grow either in planktonic (free floating) mode or sessile (attached) mode. This study focused on the optimisation of bioflocculant production by quantifying flocculation activity, determined using kaolin clay (4 g/L), by isolates prevalent in poultry slaughterhouse wastewater. Subsequent to their identification and characterisation, six bacterial strains were initially isolated from the poultry wastewater. Although all the isolated microorganisms produced bioflocculants under different conditions, i.e. pH and temperature, the strain that produced bioflocculants with a higher flocculation activity was isolate BF-3, a Comamonas sp., achieving a flocculation activity of 93.8% at 32.9 °C and pH 6.5. Fourier transform infrared spectroscopy (FTIR) analysis of the bioflocculant of the isolate, showed the presence of hydroxyl, carboxyl, alkane and amine functional groups, an indication that the bioflocculant was a protein constituent.

Perfluorooctanoate and perfluorooctane sulfonate in South African river water

This study examined the prevalence of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in river water samples (n = 56) and suspended solids (n = 5) from three major Western Cape rivers, in South Africa. Solid phase extraction (SPE) followed by liquid chromatography combined with electrospray tandem mass spectrometry (LC-MS/MS) using an analytical method developed in ISO 25101 (2009), PFOS and PFOA concentration in river water and in suspended solids from the rivers was investigated and quantified. From the results, PFOA and PFOS were detected in all the river water samples and were found in concentrations up to 314 and 182 ng/L for Diep River; 390 and 47 ng/L for Salt River; and 146 and 23 ng/L for Eerste River, respectively. In suspended solids, concentrations for PFOS and PFOA were 28 and 26 ng/g for Diep River; 16 and less than limit of detection for Eerste River; and 14 and 5 ng/g for Salt River, respectively. Some of these concentrations are higher than those previously reported in similar studies in various countries, and this suggests there is a cause for concern, in the Western Cape, South Africa, particularly in catchments where river and ground water is drawn for agricultural purposes in the province.

Susceptibility of riparian wetland plants to perfluorooctanoic acid (PFOA) accumulation

As plants have been shown to accumulate organic compounds from contaminated sediments, there is a potential for long-lasting ecological impact as a result of contaminant accumulation in riparian areas of wetlands, particularly the accumulation of non-biodegradable contaminants such as perfluorooctanoic acid (PFOA). In this study, commonly found riparian wetland plants including reeds, i.e., Xanthium strumarium, Phragmites australis, Schoenoplectus corymbosus, Ruppia maritime; Populus canescens, Polygonum salicifolium, Cyperus congestus; Persicaria amphibian, Ficus carica, Artemisia schmidtiana, Eichhornia crassipes, were studied to determine their susceptibility to PFOA accumulation from PFOA contaminated riparian sediment with a known PFOA concentration, using liquid chromatography/tandem mass spectrometry (LC/MS/MS). The bioconcentration factor (BCF) indicated that the plants affinity to PFOA accumulation was; E. crassipes, > P. sali-cifolium, > C. congestus, > P. x canescens, > P. amphibian, > F. carica, > A. schmidtiana, > X. strumarium,> P. australis, > R. maritime, > S. corymbosus. The concentration of PFOA in the plants and/or reeds was in the range 11.7 to 38 ng/g, with a BCF range of 0.05 to 0.37. The highest BCF was observed in sediment for which its core water had a high salinity, total organic carbon and a pH which was near neutral. As the studied plants had a higher affinity for PFOA, the resultant effect is that riparian plants such as E. crassipes, X. strumarium, and P. salicifolium, typified by a fibrous rooting system, which grow closer to the water edge, exacerbate the accumulation of PFOA in riparian wetlands.

Operating conditions for the continuous bioremediation of free cyanide contaminated wastewater using Aspergillus awamori

Generation of cyanide-containing wastewater is a growing problem worldwide as numerous cyanide complexes are highly unstable and degrade to form free cyanide (F-CN), the most toxic form of cyanide. Agro-waste materials, such as sweet orange (Citrus sinensis) waste from the citrus industry, are rich in readily metabolisable carbohydrates that can supplement microbial activity and thus support biodegradation of toxic compounds in wastewater. This study reports on optimal operating conditions for the continuous biodegradation of F-CN in wastewater using an Aspergillus awamori isolate in a process supported solely using C. sinensis waste extract. The optimal degradation conditions were pH 8.75 and 37.02 °C with the isolate's F-CN tolerance being observed up to 430 mg F-CN/L. Furthermore, the ammonium produced as a by-product of F-CN degradation was also metabolised by the A. awamori, with negligible residual citric acid and formate being observed in the effluent post treatment. This study demonstrates the feasibility of using agricultural waste as a primary and sole carbon source for the cultivation of a cyanide-degrading A. awamori species for F-CN degradation under alkaline conditions.

Limitations of a membrane gradostat bioreactor designed for enzyme production from biofilms of Phanerochaete chrysosporium

Growing interest has been shown in the continuous production of high-value products such as extracellular secondary metabolites used in the biotechnology, bioremediation and pharmaceutical industries. These high-value extracellular secondary metabolites are mostly produced in submerged fermentations. However, the use of continuous membrane bioreactors was determined to be highly productive. A novel membrane bioreactor, classified as a membrane gradostat reactor (MGR) was developed to immobilize biofilms to produce extracellular secondary metabolites continuously using an externally unskinned and internally skinned membrane. Anaerobic zones were identified in the MGR system when air was used for aeration. To improve the MGR system, limitations related to the performance of the bioreactor were determined using P. chrysosporium. A DO penetration depth of +/-450 microm was identified after 264 h, with the anaerobic zone thickness reaching approximately 1,943 microm in the immobilised biofilms. The penetration ratio, decreased from 0.42 after 72 h to 0.14 after 264 h. This led to the production of ethanol in the range of 10 to 56 mg/L in the MCMGR and 7 to 54 mg/L in SCMGR systems. This was attributed to an increase in beta-glucan within immobilised biofilms when an oxygen enriched aeration source was used. Increasing lipid peroxidation and trace element accumulation was observed with the use of an oxygen enriched aeration source.