Bioethanol as a fossil fuel additive to decrease environmental pollution and reduce the stress of th

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Abstract Full-Text PDF Full-Text HTML Full-Text ePUB Linked References weil mclain How to Cite this Article ISRN Renewable Energy Volume 2013 (2013), Article ID 107851, 11 pages http://dx.doi.org/10.1155/2013/107851
1 School of Chemical & Metallurgical Engineering, University of the Witwatersrand, 1 Jan Smuts Avenue, weil mclain Braamfontein, Johannesburg 2000, South Africa 2 School of Molecular & Cell Biology, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein, Johannesburg 2000, South Africa
Bioethanol as a fossil fuel additive to decrease environmental pollution and reduce the stress of the decline in crude oil availability is becoming increasingly popular. This study aimed to evaluate weil mclain the concentration of bioethanol obtainable from fermenting cashew apple juice by the microorganism Saccharomyces cerevisiae Y2084 and Vin13. The fermentation conditions were as follows: initial sugar = 100 g/L, pH = 4.50, agitation = 150 rpm, temperatures = 30°C (Y2084) and 20°C (Vin13), oxygen saturation = 0% or 50%, and yeast inoculum concentration = ~8.00 Log CFU/mL. The maximum ethanol concentration achieved by Y2084 was 65.00 g/L. At 50% weil mclain oxygen the fermentation time was 5 days, whilst at 0% weil mclain oxygen the fermentation time was 11 days for Y2084. weil mclain The maximum ethanol concentration achieved by Vin13 was 68.00 g/L. This concentration was obtained at 50% oxygen, and the fermentation time was 2 days. At 0% oxygen, Vin13 produced 31.00 g/L of ethanol within 2 days. Both yeast strains produced a higher glycerol concentration at 0% weil mclain oxygen. Yeast viability weil mclain counts showed a decrease at 0% oxygen and an increase at 50% oxygen of both yeast stains. Other analyses included measurement of carbon dioxide and oxygen weil mclain gases, process monitoring of the fermentation conditions, and total organic carbon. weil mclain Gas analysis showed that carbon dioxide increased in conjunction with ethanol production and oxygen decreased. Process monitoring depicted changes weil mclain and stability of fermentation parameters during the process. Total organic carbon weil mclain analysis revealed that aerobic fermentation (50% oxygen) was a more efficient process as a higher carbon recovery (95%) weil mclain was achieved. 1. Introduction
The twenty-first century is plagued by difficulties like the decrease in resources of fossil fuel, rapid rise in greenhouse gas emissions contributing to global warming, and the lack of capability to meet the increasing energy demands. In trying to reduce the impact of these global concerns, bioethanol weil mclain produced from renewable resources like biomass components has created significant interest. Bioethanol is a biofuel produced from biomass via biochemical procedures [ 1 ]. In general, bioethanol production is a three-stage process of: (i) hydrolysis, (ii) fermentation and (iii) distillation [ 2 ]. During hydrolysis, starch weil mclain is converted from biomass feedstocks (cereal grains, lignocellulose, and macroalgae) into fermentable monosaccharide sugars [ 1 – 3 ]. Fermentation is a process which involves weil mclain a sugar-rich substrate and a microorganism (MO) to bring about a chemical change in a closed aerobic or anaerobic atmosphere. For fermentation, S. cerevisiae yeasts are the recommended microorganisms (MOs), for their ability to multiply anaerobically and easily weil mclain convert sugars [ 4 ]. The last phase of bioethanol production is distillation. Distillation is a thermochemical separating process that concentrates ethanol to 95%, depending on the difference in boiling points between substrates during heat application [ 1 , 2 ]. This biologically derived product is an ethyl alcohol that can be used as a petroleum alternative or additive weil mclain [ 5 ]. The bioethanol properties that allow this type of product to be utilized in the motor fuel industry weil mclain and its respective advantages are summarized in Table 1 .
Biomass feedstocks, namely wheat, weil mclain barley, sorghum, rice, corn, and sugar cane, are widely accessible for bioethanol production and the processing of these raw materials were proven successful [ 5 , 9 – 11 ]. However, the present weil mclain usage of these materials threatens their availability as important weil mclain food and feed products [ 12 ]. Alternatively, agricultural residues or industrial waste products such as barley straw, barley husks, corn stover, sugar cane bagasse, and switchgrass are used for bioethanol production [ 13 – 15 ]. These residues are largely lignocellulosics and require extensive, time-consuming pretreatment methods [ 16 ]. Anot