PRODUCTION OF ETHANOL FROM CASSAVA (MANIHOT ESCULENTA)
A literature review of ethanol production from local materials especially from cassava is presented.
The study was carried out to investigate the production of a good quality ethanol from cassava using microorganisms. The microorganisms used were malt and yeast (saccharomyces cerevisiae). The other intermediate production was starch and sugar which ethanol was obtained in a satisfactory yield and purity (about 98%). It is therefore not 100% ethanol.
Ethanol is produced commercially by chemical synthesis and fermentation. Practically all industrials ethanol is manufactured synthetically from petroleum and natural gas while all beverage alcohol is produced by fermentation of cereal grains molasses, potatoes and other materials with high starch and sugar contents.
Potentials sources of production of alcohol in Nigeria include millet, yam, sorghum, corn, cocoyam and cassava. Cassava tuber (manihot esculenta) is the most potential candidate by virtue of the fact that this crop can be grown with low level of management and also varieties for industrials production and presence of high yielding cultivars.
Cassava (manihot esculenta) also called manioc of the spurge family (Euphorbiaceae) is native from South Africa but is now cultivated in most tropical and subtropical regions. It is a shrubby perennial about 9ft high and has terminal starchy tuberous root. The root contain prussic acid and some are quite poisonous but heat expels the volatile acid and render the materials harmless.
The hydrolysis of cassava and utilization of an efficient low cost saccharifying agent are factors of paramount importance in the production of food or alcohol from cassava starch since this polysaccharide must be broken down into fermentation sugar which can be utilized by the micro- organisms.
The amylolytic enzymes used in the biological saccharification can be obtained from several sources. These include COM, and barley malt and the surface and submerged fungal and bacteria culture processes.
The breakdown of gelatinized starch occur via the hydrolysis of the – 1.4 linkages which from the glucose molecules and also via the hydrolysis of – 1,6 amylopectin component of starch. Malt contain the three most important enzymes for the starch breakdown – amylase. B – amylase and amyloglucosidase.
Ethanol (ethyl alcohol) is produced by the anaerobic fermentation of the saccharified starch (reducing sugar) by yeast via the embden – meyerhoff – parnas (EMP) pathway of anaerobic fermentation. Saccharomyces cerevisiae was chosen for such characteristics as their ability to ferment rapidly and to tolerate higher ethanol concentration and to flocculate easily.
Ethyl alcohol is colorless, volatile liquid, which is flammable and toxic and has a pungent taste. It boils 78.4oc and melts at –112. 3oc, has a specific gravity of 0.7851 at 20oc and insoluble in water and most organic liquid. The general formula of ethanol is CNH2NHOH.
HISTORICAL BACKGROUND OF ETHANOL
The name “alcohol” is a generic name derived from two Arabic words, al and koli which were used to described a finely ground powder used by oriental women to darken their eye brow. The name was generally restricted to alcohol spirits of wine rectified to the highest “degree”.
Ethyl alcohol is of course extremely well known as a constituent of alcohols beverage distilled; beer, wine. The world alcohol unqualified is often used to refer to ethyl alcohol.
As a beverage, it has been produced and utilized unknowingly as far back as 4000 year ago by the pharaohs in Egypt.
An indication of the antiquity of the knowledge of the effect of ethyl alcohol has been traced to Noah, who built for himself a vineyard and grew which he fermented into a sort of alcohols beverage on which he became drunk with unfortunate result to his respectability. Other (1967).
Williams and Lansford described alcoholic fermentation as the process by which certain micro- organism, particularly strains of yeast convert sugar to a mixture of ethanol (ethyl alcohols) and carbon dioxide.
The term fermentation (Latin fermentation to boil) was used to describe the appearance of boiling due to evolution of gas caused by microbiological reactions. The microorganism were originally named organized ferments to distinguish them from unorganized ferments that had been extracted from plants and animals.
The term enzyme (Greek en, in, zyme. Yeast) came into general use after sometime and soon displaced the term ferment. Fermentation has come to mean enzymatic action other than those involving oxygen. The alcoholic fermentation of sugars was almost certainly discovered by accident, probably as a result of some cereal infusion becoming infested with yeasts and other micro – organisms. The discover is thought to have taken place well over ten thousand year ago among the ancient civilization inhabiting in nice valley.
The most ambitions step so far taken is in Brazil, which is the highest probably and most advanced in the world and it aims at having ethanol from came.
The ethanol produced by alcoholic fermentation is responsible for much of the desired potency in an alcoholic beverage but of the more subtle quantities of taste and aroma are caused by quantitatively mirror product of the yeast fermentation particularly higher alcohols and esters of these alcohols.
AIMS AND OBJECTIVE OF THE PROJECT
This project is general at investigating the possibilities of using cassava manihot esculenta a local raw materials as a chief stock to produce ethanol which are industrially and humanly useful.
1.3 STATEMENT OF PROBLEMS
The problems, which arise as a result of high cost of importation and harsh economic situation in the country, it becomes imperative to search for local raw materials to replace the imported ethanol by using cassava, which yield high quality of starch for the production of alcohol.
Ho. Effect of prussic acid and cyanogenic acid present in cassava.
H1. There is no effect of the prussive and cyanogenic acid in the ethanol production because during the process of heating, the volatile acids escaped out and therefore the materials becomes harmless.
At present there is no commercial production of alcohols from cassava in Nigeria. Huge amount of money are being spent to import ethanol for medical pharmaceutical, research and industries. It will be economically useful if government imitate a move towards the direction of producing ethanol from our local raw materials (cassava).
This study is limited to small-scale production because of limited raw material compare to industrial scale. And due to small scale and non-availability of chemicals, some useful determination cannot be carried out.