Bio-energy

[dgncan]

Saccharomyces cerevisiae bakterisi kullanılarak sukroz şekerinden ethanol üretimi hakkında Ege üniversitesi öğrencileri tarafından yapılan bir çalışma.





Comparison of Dierent Production Processes for
Bioethanol
BelIs CAYLAK
Ege University, Ege Technical Highschool
Bornova, _Izmir - TURKEY
Fazilet VARDAR SUKAN
Ege University, Faculty of Chemistry Engineering
Bornova, _Izmir - TURKEY
Received 25.04.1996
In this study, ethanol was produced with the microorganism Saccharomyces cerevisiae by using sucrose
as a substrate. Batch processes were tested by using the same substrate, microorganism and medium
composition. Saccharomyces cerevisiae, used in the free form in the rst group of experiments, was
immobilized by dierent methods. In the second group of experiments agar, sponge and a natural
material called lua cylindrica ber were used as support materials. The batch processes with free and
immobilized microorganisms were compared with respect to eciency and yield.
Introduction
The decreasing reserves and increasing value of petrochemicals have renewed the interest in the production
of bioethanol and its use as fuel and chemical feedstock.
Ethanol can be produced from many dierent raw materials, which are grouped according to the
type of carbohydrates they contain, i.e., sugar, starch or cellulose. Sugar for ethanol production (sucrose,
glucose or fructose) may be derived from any of the three classes of raw materials1 . Industrial processes
for the production of ethanol by fermentation of molasses, beet, cane or grain sugars are well established.
Since sugars are already available in a degradable form and yeast cells can metabolize sugars directly, these
substrates require the least costly preparation. The other carbohydrates must be hydrolyzed to sugars before
they can be metabolized. So, although starchy or cellulosic materials are cheaper than sugar-containing
raw materials, the requirement of converting the starch or cellulosic materials to fermentable sugars is a
disadvantage of these substrates2 .
Ethanol can be produced by four main types of industrial operations: batch, continuous, fed-batch
and semi-continuous3 .
In batch fermentation, substrate and yeast culture are charged into the bioreactor together with
nutrients3 . Most of the ethanol produced today is done by the batch operation since the investment costs
are low, do not require much control and can be accomplished with unskilled labor. Complete sterilization
and management of feedstocks are easier than in the other processes.





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