Simulated Inhibitory Effects of Typical Byproducts of Biomass Pretreatment Process on the Viability of Saccharomyces cerevisiae and Bioethanol Production Yield

The abundance of second generation feedstock reinforces the consideration of biofuel over fossil fuel, as bioethanol can be produced from lignocellulosic materials. However, the pretreatment required for oxidation of lignocellulose into hexose often results in the production of inhibitors likely to impede the activity of Saccharomyces cerevisiae during bioethanol production. This study aimed to investigate the comparative inhibitory effects of acetic acid and vanillin on the viability of S. cerevisiae and the production yield of bioethanol. Different concentrations of inhibitors were spiked in the fermentation broth then the production of bioethanol monitored overtime and correlated with cell viability. The results showed that the inhibition of S. cerevisiae by vanillin is more potent compared to acetic acid; however the reduction of bioethanol yield after 12 h was more pronounced with acetic acid (42.8% reduction) than with vanillin (33.3% reduction) which was ascribed to the simultaneous production of weak acids during the fermentation process. The viability test has shown that in the presence of lower concentrations of inhibitors, S. cerevisiae can adapt for the first 12 h of fermentation and then may improve ethanol production yield overtime. At lower concentrations (2 g/l vanillin and 4 g/l acetic acid) the effect of inhibitors on the viability of S. cerevisiae and ethanol productivity does not last and can be overcome by the adaptation of the yeast. However, the presence of higher concentrations (4 g/l vanillin and 6 g/l acetic acid) results to nearly total inhibition of bioethanol production and the remediation of such effect may therefore require a detoxification process.Keywords: Bioethanol Production, Saccharomyces cerevisiae, Inhibition, Acetic Acid, Vanillin, Cell Viabilit

Exposure of rural households to toxic cyanobacteria in container-stored water

Cyanobacteria are potent producers of cyanotoxins that may present a health risk to people. This is especially important in rural areas where people use untreated surface water, containing cyanobacteria, for household purposes including cooking and drinking. Water is collected from these sources mainly in plastic containers, transported home and stored during use. This study investigated the occurrence of cyanobacteria and their associated toxins in these containers as well as in the associated surface water sources. The results suggest that cyanobacteria are transferred from the water sources to the containers and then survive and possibly grow in biofilm forming inside the vessels. Their associated cyanotoxins were not found in any health-significant quantities in containers. However, the occurrence of cyanobacteria in the water used by the households collected in containers clearly indicates that it can be an important route of exposure especially if toxic cyanobacteria are present in the source water. In several cases a risk of cyano-intoxication might exist unless the households undertake preventative measures.Keywords: cyanobacteria, cyanotoxin, microcystin, surface water sources, drinking water containers, biofil

Assessing the effectiveness of a biological recovery of nickel for tailing dumps management

The mobilization of nickel from sulphide minerals using sulfuric acid and heterotrophic microorganism (Bacillus subtilis) was independently examined. The influences of parameters such as the concentration of acid and bacteria as well as reaction time were considered. Results of the monod-type kinetic study showed faster recovery of nickel from tailings (20 ppm/h) than from ore (8.07 ppm/h) by biological mobilization and similar trend with sulfuric acid

Application of solar treatment for the disinfection of geophagic clays from markets and mining sites

Most of the microorganisms occurring in geophagic clays are undesirable and may to some extent be harmful to geophagists; it is therefore important to develop a cheap and sustainable technique for the treatment of these clays prior to consumption. In this study, a solar treatment simulated in a chamber has been investigated for its potential to inactivate the microorganisms found in the geophagic clays obtained from mining sites and from the markets. The results have shown that irrespective of the sources of the clays, they were contaminated with large amount of potentially harmful microorganisms which could have been sustained by suitable conditions such as relatively high moisture content (average of 3.6%) and the presence of organic carbon (between 1.06 and 1.5%). Treatment with simulated solar irradiation has resulted in most instances to the reduction of the number (up to 100% inactivation) of microorganisms although in few cases the same conditions have stimulated the growth of some dormant microorganisms including Bacillus subtilis, Paenibacillus, Bacillus cereus, Bacillus thuringiensis, Bacillus humi and Arthrobacterarilaitensis. This study shows that the solar treatment has the potential to significantly reduce the amount of microorganisms occurring in the geophagic clays, but require further investigation for improvement of the technique.Keywords: Geophagic clays, solar treatment, microorganisms, moisture content, organic carbon, mining sites, market

The next step in the bioremediation of heavy metal polluted water: development of suitable microbial-sorbent

Abstract In this study needful changes are inflicted on potential microbial sorbent in order to facilitate it use industrially for remediation of heavy metal pollution of water sources. Bacillaceae bacterium isolated from mining areas was transformed with cnr gene coding for nickel and cobalt resistance. Nickel recovery ability of the wild strain was then improved and prediction of adsorption behaviour made possible

Review of challenges in the escalation of metal-biosorbing processes for wastewater treatment: Applied and commercialized technologies

Despite the eminent consequences, wastewaters containing toxic heavy metals are still discharged in the environment without prior treatment, certainly because of the high cost associated with the effective management of these effluents. Difficulties emanated from the fact that most of the technologies available for the remediation of the pollution require high capital and operational cost, which cannot be justified for the treatment of diluted effluents. Biosorption technique for its relatively competitive cost has been immensely investigated in laboratories for remediation of heavy metals polluted effluents. This paper reviews the major progresses achieved in the field of biosorption technology since it was first introduced; enhancement of the performance of suitable biosorbents through regeneration and immobilization techniques are some of the approaches that have contributed to improve metal removal processes. Despite some few progresses, efforts devoted in the development of biosorption technology have not been translated into successful implementation everywhere, hence, the persistence of problems related to pollution of water sources by toxic heavy metals in most part of the world. Challenges hindering the commercialization of biosorption technology are clearly discussed and critical aspects related to the characteristics of waste effluents and potential of biosorbents are highlighted. Suggestions are made for consideration of hybrid technologies, carefully designed and informed by the complexity of waste effluents.Keywords: Mine waste, toxic heavy metals, biosorption technology, immobilization, desorption, hybridization of techniques, escalation of processesAfrican Journal of Biotecnology, Vol 13(17), 1756-177

Copolymerization of ethyl acrylate onto guar gum for the adsorption of Mg(II) and Ca(II) ions

In the present study, the copolymerization of ethyl acrylate and guar gum was induced by microwave irradiation in the presence of catalytic amount of the initiator potassium persulfate (KPS). The maximum percentage conversion was found to be 107.1% under microwave power of 900 MW after 3 min exposure. The copolymerized guar gum-graft-poly-ethyl acrylate (GG-g-PEA) was characterized using FTIR spectroscopy and SEM analysis. The effect of pH on the capacity of the GG-g-PEA copolymers to reduce the hardness of the water was investigated, leading to the effective removal of Ca(II) and Mg(II) ions from solutions at pH 8. The calculated values of the coefficient of determination (0.914–0.9553) for Ca(II) and Mg(II), respectively, showed that the equilibrium isotherm data followed the Freundlich isotherm model. The pseudo-second-order model was suitable for the modelling of the kinetic data, predicting adsorption capacities of 0.2680 g/mg/min for Ca(II) and 0.3835 g/mg/min for Mg(II), respectively. The synthesized GG-g-PEA adsorbent could therefore be recommended for the reduction in the water’s hardnes