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Production of bioethanol from cassava and sweet potato peels.


Bioethanol is a microbiological way of converting simple sugar into ethanol and carbodioxide (C[O.sub.2]) [6]. Bioethanol is a principal fuel that can be used as petrol substitute for vehicle [4]. It is a renewable energy Renewable energy utilizes natural resources such as sunlight, wind, tides and geothermal heat, which are naturally replenished. Renewable energy technologies range from solar power, wind power, and hydroelectricity to biomass and biofuels for transportation.  source produced mainly by sugar fermentation process, although it can also be manufactured by the chemical process of reacting ethylene with steam [3]. The main sources of sugar required to produce ethanol come from fuel or energy crops [11]. These crops include maize, cassava cassava (kəsä`və) or manioc (măn`ēŏk), name for many species of the genus Manihot of the family Euphorbiaceae (spurge family).  and cassava products, wheat crops, waste straw, guinea corn husk, rice husk, millet millet, common name for several species of grasses cultivated mainly for cereals in the Eastern Hemisphere and for forage and hay in North America. The principal varieties are the foxtail, pearl, and barnyard millets and the proso millet, called also broomcorn millet  husk, sawdust and sorghum sorghum, tall, coarse annual (Sorghum vulgare) of the family Gramineae (grass family), somewhat similar in appearance to corn (but having the grain in a panicle rather than an ear) and used for much the same purposes.  plant. Ethanol is a high octane fuel and has replaced lead as an octane enhancer in petrol [17].

By blending ethanol with gasoline we can also oxygenate the fuel mixture so it burns more completely and reduces pollution emission. Ethanol fuel

    Ethanol fuel is ethanol (ethyl alcohol), the same type of alcohol found in alcoholic beverages. It can be used as a fuel, mainly as a biofuel alternative to gasoline, and is widely used in cars in Brazil.
     trends are widely sold in the United State. The most common blend is 10% ethanol and 90% petrol ([E.sub.10]) and vehicle engines require no modification to run on [E.sub.10] and vehicle warranties are unaffected also [14]. Ethanol derived from biomass is the only liquid transportation fuels that do not contribute to the green house gas effect [15,12,3]. Ethanol has been produced in batch fermentation with fungi strains such as Aspergillus niger Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food. , Mucor mucedo, Saccharomyces Saccharomyces: see yeast.  cerevisiae that cannot tolerate high concentration of ethanol [13,18,22].

    The objective of the study is to produce bioethanol from sweet potatoes peels and cassava peels through fermentation using Saccharomyces ceevisiae and Zymomonas mobilis Zymomonas mobilis is a bacterium belonging to the genus Zymomonas. It is notable for its bioethanol-producing capabilities, which surpass yeast in some aspects. It was originally isolated from alcoholic beverages like the African palm wine, the Mexican pulque, and also as a .

    Materials And Methods

    Samples Collection:

    Four hundred grams (400 g) each of sweet potatoe peels and cassava peels were collected from Kasuwa Gwari market wastes dump site in Minna. These were asceptically collected in a polythene bag and taken to Microbiology laboratory of Federal University of Technology, Minna, Niger State, Nigeria, for further analysis.

    The organisms used were Gloeophyllum sepiarium, Pleurotus ostreatus, Zymomonas mobilis and Saccharomyces cerevisiae. These were collected from stock cultures of Microbiology Laboratory of Federal University of Technology, Minna, Niger State, Nigeria. The cultures were characterized and confirmed using morphological and biochemical methods described by Domsch and Gams [7], Holts, et al. [9], Obire [16], Cheesbrough [5], Oyeleke and Manga [19].

    Bioethanol Production:

    The methods used for Bioethanol production includes; enzyme hydrolysis hydrolysis (hīdrŏl`ĭsĭs), chemical reaction of a compound with water, usually resulting in the formation of one or more new compounds. , fermentation and distillation process.

    Enzyme hydrolysis:

    Different quantities of the substrates was weighed inside separate 500 c[m.sup.3] conical flasks; carried out in quadruple (i.e.20 grams each in four different conical flaks, 35 grams each in another sets of four conical flasks and 50 grams in another four different conical flasks). Sterile distilled water was added to make up to the mark and the flasks were plunged with sterile cotton wool wrapped in aluminium foil to avoid contamination. The mixtures were sterilized in an autoclave autoclave

    Vessel, usually of steel, able to withstand high temperatures and pressures. The chemical industry uses various types of autoclaves in manufacturing dyes and in other chemical reactions requiring high pressures.
     at 121[degrees]C for 15 minutes, allowed to cool and sterile distilled water was aseptically added to make up to mark again. Freshly harvested cells of Gloeophyllum sepiarium was inoculated into a set of 20 grams, 35 grams and 50 grams of each substrates mixture under aseptic aseptic /asep·tic/ (-tik) free from infection or septic material.

    Of, relating to, or characterized by asepsis.
     condition. Pleurotus ostreatus was also added aseptically to another set of each of the substrate mixtures (20 g, 35 g and 50 g). Gloeophyllum sepiarium and Pleurotus ostreatus was added into another set of the flasks containing the mixtures while the other set serves as control for the two substrates. The flasks were covered and were then incubated at room temperature (28[degrees]C) for seven days. The flasks were shaken at interval to produce a homogenous homogenous - homogeneous  solution and even distribution of the organisms in the substrates mixture. The mixtures were separately filtered after seven days using No 1 Whatman filter paper.


    Supernatant supernatant /su·per·na·tant/ (-na´tant) the liquid lying above a layer of precipitated insoluble material.


    the liquid lying above a layer of precipitated insoluble material.
     from the above hydrolysis process were transferred into another sets of conical flasks correctly labelled, covered, autoclaved at 121[degrees]C for 15 minutes and allowed to cool. Freshly harvested cells of Zymomonas mobilis was aseptically added into a set of flasks containing the hydrolysed supernatants (20 g, 35 g and 50 g supernatants) and Saccharomyces cerevisiae was also added into another set of hydrolysed supernatant. The two organisms were combined into the third set of the hydrolysed supernatants while the control set still served as control. The flasks were corked using cotton wool, shake and incubated at room temperature (28[degrees]C [+ or -] 2[degrees]C) for five days. The flasks were shaken at interval to produce a homogenous solution and even distribution of the organisms in the substrates mixture.


    This was carried out at using distillation apparatus (set up). The fermented liquid was transferred into round bottom flask and placed on a heating mantle fixed to a distillation column enclosed in running tap water. Another flask was fixed to the other end of distillation column to collect the distillate dis·til·late
    A liquid condensed from vapor in distillation.


    a product of distillation.
     at 78[degrees]C (standard temperature for ethanol production). This was done for each of the fermented broth.

    Determination of Quantity of Ethanol Produced:

    The distillate collected was measured using a measuring cylinder and expressed as quantity of ethanol produced in g/l by multiplying the volume of the distillate by the density of ethanol (0.8033 g/[cm.sup.3]) [10].

    Determination of Ethanol Concentration:

    Ethanol concentration was determined by comparing the density of the ethanol produced with the standard ethanol density curve. Standard ethanol curve was obtained by taking series of percentage (v/v) ethanol (10%, 20%, 30%, 40% and 50%) solution which were prepared in a 100 ml volumetric flask and the weights were measured as described by Amadi, et al. [2], Oyeleke and Jibril [20]. The density of each of the prepared ethanol solution was calculated and a standard curve of density against percentage ethanol (v/v) was plotted.


    Bioethanol Produced from Cassava Peel:

    Table 1 shows the volume ([cm.sup.3]), mass (g/[cm.sup.3]) and percentage yield of biethanol (%) of bioethanol produced from cassava peel when hydrolysed with Gloeophyllum sepiarium and Pleurotus ostreatus and fermented with Zymomonas mobilis and Saccharomyces cerevisiae. Maximum yield of 11.97 g/[cm.sup.3] with a concentration of 26% was produced from cassava peel when S. cerevisiae and Z. mobillis was used for fermentation.

    Bioethanol Produced from Sweet Potato Peels:

    Table 2 shows the volume ([cm.sup.3]), mass (g/[cm.sup.3]) and percentage yield (%) of bioethanol produced from sweet potato peel as a result of enzyme hydrolysis with Gloeophyllum sepiarium and Pleurotus ostreatus and fermention with Zymomonas mobilis and Saccharomyces cerevisiae. 6.5 g/[cm.sup.3] with a concentration of 12% was the highest yield of ethanol produced.


    The enzymatic production of bioethanol from cassava and sweet potato peels was analysed using Gloephyllum sepiarium and Pleurotus ostreatus to hydrolyse Verb 1. hydrolyse - undergo hydrolysis; decompose by reacting with water

    change - undergo a change; become different in essence; losing one's or its original nature; "She changed completely as she grew older"; "The weather changed last night"
     the substrates and fermented with Zymomonas mobilis and Saccharomyces cerevisiae. The result revealed that Z. mobilis has a maximum yield of ethanol (10.6 g/[cm.sup.3]) and from 5.9 g/[cm.sup.3] from cassava peels and sweet potato peels respectively while S cerevisiae has a maximum yield of 10.36 g/cm3 and 5.78 g/[cm.sup.3] from cassava and sweet potato peels respectively; this result reveals a higher production by Z. mobilis than S. cerevisiae. This may be because Z. mobilis posseses pyruvate decarboxylase and alcohol dehydrogenase alcohol dehydrogenase /al·co·hol de·hy·dro·gen·ase/ (ADH) (de-hi´dro-jen-as) an enzyme that catalyzes the reversible oxidation of primary or secondary alcohols to aldehydes; the reaction is the first step in the metabolism of alcohols by  as reported by Gunasekran and Chandra [8] as the key enzymes in ethanol production and they tends to facilitate continuation of fermentation at high concentration of ethanol, they also stated that comparative laboratory- and pilot-scale studies on kinetics of batch fermentation of Z. mobilis versus a variety of yeast have indicated the suitability of Z. mobilis over yeasts due to its higher sugar uptake and ethanol yield, its lower biomass production and its higher ethanol tolerance, all these might be responsible for high ethanol produced from both cassava and sweet potato peels. When the organisms were mixed, maximum bioethanol yield of 11.97 g/[cm.sup.3] (26%) for cassava peel and 6.5 g/[cm.sup.3] (12%) for sweet potato peel was produced and these could be because the two organisms have potential to produce ethanol which makes them produce more when in combination than when used separately.

    The result also revealed maximum yield of ethanol 12 g/[cm.sup.3] (26%) for cassava peel and 6.5 g/[cm.sup.3] (12%) for sweet potato peels respectively. This could be due to presence of more carbohydrate which could be fermented to ethanol in cassava peels than in sweet potato peels.

    Average ethanol yield (concentration) of 17.6% produced from cassava peels is more than the average ethanol yield (concentration) reported by Agunlejika, et al. [1] who reported an average ethanol concentration of 16% from spoilt mangoes. This is likely due to presence of more carbohydrate content in cassava peel than in spoilt mangoes. But this agreed with Oyeleke, et al. [21] who reports an average ethanol yield (concentration) of 17.6% from spoilt fruits.

    Average ethanol yield (concentration) of 9.3% produced from sweet potato peel is in contrast with Agunlejika, et al. [1] who reported average ethanol yield (concentration) of 16% from spoilt fruits and Oyeleke and Jubril [20], who reported percentage ethanol concentration of 67.7% and 63.8% as observed when A. niger and Z. mobilis were used simultaneously on guinea corn husk and millet husk respectively. This could be because of more carbohydrates content in spoilt mango, guinea corn husk and millet husk than in sweet potato peels.

    The result of this study confirmed that ethanol can be produced from cassava and sweet potato peels which are agricultural wastes. More ethanol was produced from cassava peels than from sweet potato peels, thus making cassava peel a better alternative to sweet potato peel, as well as spoilt fruits. The use of cassava and cassava peels is a worthwhile venture for ethanol production; considering their cost and because it is a means of controlling environmental pollution since bioconversion bi·o·con·ver·sion  
    The conversion of organic materials, such as plant or animal waste, into usable products or energy sources by biological processes or agents, such as certain microorganisms.
     of cellulosic biomass into fermentable fermentable,
    adj the ability to undergo a chemical reaction in the presence of an enzyme that results in the creation of either acid or alcohol; in the oral cavity, the ability to create acid in plaque.
     sugar for production of ethanol was done using cellulose degrading microorganisms, thus making bioethanol production economical and environmentally friendly and also renewable.


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    (1) Oyeleke, S.B., (2) Dauda, B.E.N., (1) Oyewole, O.A., (3) Okoliegbe, I.N. and (1) Ojebode, T.

    (1) Department of Microbiology, Federal University of Technology, Minna, Nigeria.

    (2) Department of Chemistry, Federal University of Technology, Minna. Nigeria

    (3) Department of Microbiology, University of Abuja The University of Abuja was established on January 1, 1988 (under decree NO. 110 of 1992 as amended) as a dual mode university with the mandate to run both conventional and distance learning programmes and was the first university in Nigeria to assume such dual mandate thus , Nigeria

    Corresponding Author

    Oyeleke, S. B., Department of Microbiology, Federal University of Technology, Minna, Nigeria.
    Table 1: Bioethanol Produced from Cassava Peel.
    Qty (g)   Microorganisms                            Volume of
              Hydrolysis        Fermentation      Produced ([cm.sup.3])
    20        G. sepiarium      S. cerevisiae              8.4
    20        P. ostreatus      Z. mobillis                9.1
    20        G. sepiarium      S. cerevisiae
                     +                 +                   9.7
              P. ostreatus      Z. mobillis
    35        G. sepiarium      S. cerevisiae              9.0
    35        P. ostreatus      Z. mobillis               11.0
    35        G. sepiarium      S. cerevisiae
                     +                 +                  12.0
              P. ostreatus      Z. mobillis
    50        G. sepiarium      Z. mobillis               13.2
    50        P. ostreatus      S. cerevisiae             12.9
    50        G. sepiarium      S. cerevisiae
                     +                 +                  14.9
              P. ostreatus      Z. mobillis
              Mass of Bioethanol    percentage yield
                (g/[cm.sup.3])           (Conc)
    20              6.75                  12
    20              7.31                  13
    20              7.80                  14
    35              7.23                  12
    35              8.84                  16
    35              9.64                  20
    50             10.60                  23
    50             10.36                  22
    50             11.97                  26
    Table 2: Bioethanol Produced from Sweet Potato Peel.
    Qty (g)   Microorganisms                     Volume of Bioethanol
              Hydrolysis fermentation            Produced ([cm.sup.3])
    20        G. Sepiarium      S. cerevisiae             4.2
    20        P. ostreatus      Z. Mobillis               5.4
    20        G. sepiarium      S. cerevisiae
                     +                 +                  5.8
              P. ostreatus      Z. Mobillis
    35        G. sepiarium      S. cerevisiae             5.7
    35        P. ostreatus      Z. mobillis               5.9
    35        G. sepiarium      S. cerevisiae
                     +                 +                  6.6
              P. ostreatus      Z .mobillis
    50        G. sepiarium      Z. mobillis               7.4
    50        P. ostreatus      S. cerevisiae             7.2
    50        G. sepiarium      S. cerevisiae
                     +                 +                  8.1
              P. ostreatus      Z. Mobillis
    Qty (g)   Mass of Bioethanol    Percentage Yield
                (g/[cm.sup.3])         (conc) (%)
    20              3.37                   6
    20              4.34                   6
    20              4.66                   9
    35              4.58                   7
    35              4.74                  10
    35              5.30                  10
    50              5.90                  12
    50              5.78                  12
    50              6.51                  12
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    Title Annotation:Original Article
    Author:Oyeleke, S.B.; Dauda, B.E.N.; Oyewole, O.A.; Okoliegbe, I.N.; Ojebode, T.
    Publication:Advances in Environmental Biology
    Article Type:Report
    Geographic Code:6NIGR
    Date:Jan 1, 2012
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