Potentials of Potato Starch for Biofuel Production. Fermentative Production of Alcohol by Saccharomyces Cerevisiae utilizing Potato Starch

Scientific Study, 2014

7 Pages




I. Raw Material
II. Microorganism used
III. Conversion of starch to glucose by acid hydrolysis method
IV. Enzymatic conversion of starch to glucose
V. Optimization of temperature for alcohol production







In present World, both price and availability of crude oil have motivated worldwide search for cheap alternatives. Starch is an alternative source of energy because it is both renewable and available throughout the globe in large quantities. There are varieties of products which can be obtained from starch biomass via hydrolysis. Alcohol is one of the largest volumes of products that can be produced from biomass. Recently there has been active research aimed at attaining an increase in ethanol productivity by fermentation. Large amount of potato is wasted every year due to improper cold storage facilities in developing and underdeveloped countries. So, saccharification and conversion of these huge amounts of excess potatoes into alcohol, especially ethanol may generate employment potential apart from saving good amount of foreign exchange. In my present research work, production of alcohol from different varieties of potato, showed a better result after enzymatic hydrolysis of those potatoes followed by alcohol(ethanol) production utilizing Saccharomyces cerevisiae NCIM 3314. Maximum alcohol(ethanol) was obtained utilizing high grade Kufri Jyoti variety when compared to other varieties of potatoes.

Key words: Potato, starch, diastase, saccharification, Saccharomyces cerevisiae, ethanol.


The usual sources of raw material for alcohol production from starch are cereals, grains such as corn, wheat, rye, barley, milo (sorghum grains),rice etc. Other types of starch are available from potatoes of all kinds [1].The amount of alcohol produced from potato starch can vary with the variety of potatoes such as Kufri Chandramukhi, Kufri Jyoti, Kufri Nainital etc.

Generally, potato contains 12-17 % of starch. The size of starch granules present in potato tuber cells ranges from 5-100 micrometers. These granules contains little amount of water, organic & mineral substances other than starch. The distribution of starch in potato tuber is uneven. The cells close to vascular system carries more starch than the cells nearer to the cortex. Smallest amount of starch develops in the pith [2-3].

Alcohol like ethanol can be produced from potato starch through fermentation process. Fermentative production of ethanol as an alternative to petroleum is gaining importance due to the realization of diminishing natural oil & gas resources [4]. Apart from the prime alternatives to petrol(gasohol; 80% gasoline + 20% ethanol), ethanol is also used as a solvent & is a versatile feedstock, used to produce various organic chemicals & their derivatives [5].

For production of alcohol from potato starch by fermentation, yeast S.cerevisiae plays an important role. But this microorganism cannot utilize starch as such, so conversion of starch to fermentable sugar is needed which can be easily utilize by S.cerevisiae for production of alcohol. This can be done either by acid hydrolysis or by enzymatic hydrolysis.

Acid hydrolysis is relatively simple, but it requires acid proof equipment, high temperature and handling of acid. Due to these reasons, it is not frequently used in small scale production, but for large scale production it is an ideal process. Acids also cost lesser than enzymes, thus financial requirements can be reduced, which is another useful factor in large scale production.

Although conventional process still utilizes glucose from starch by acid hydrolysis prior to production of alcohol, enzymatic hydrolysis [6] of potato starch improves both process efficiency and product quality, which are ideal factors for small scale production of alcohol.

Considering the above factors, study was carried out on production of alcohol using Saccharomyces cerevisiae from sugar(glucose) obtained by hydrolysis of potato.


I. Raw Material

Potato (Solanum tuberosum) was chosen as raw material in the present study. For the present study different varieties of potatoes were procured from the local market and they were peeled, cut into small pieces & boiled for 20 minutes. Later they were mashed and made to slurry with distilled water [10% (wt/vol)].

II. Microorganism used

The microorganism Saccharomyces cerevisiae NCIM 3314 was maintained on agar slant containing glucose 1%, peptone 0.5%, yeast extract 0.3%, malt extract 0.3% and agar 2% with a pH 4.5. After the growth it was stored at 4°C.

A loopful of S.cerevisiae ( 24 hrs. old ) culture was transferred to inoculum media & incubated(stationary) at 28±2°C for 24 hours with 120 rpm shaker speed.

III. Conversion of starch to glucose by acid hydrolysis method

Hydrolysis was done using slurry of potato(10% wt/vol). To this slurry conc. HCl was added & hydrolyzed for half an hour.

IV. Enzymatic conversion of starch to glucose

Slurry of boiled 10% (wt/vol) peeled potato was prepared & 1% (wt/vol) Diastase enzyme was added. The starch-enzyme slurry was incubated at 35±2°C for 24 hrs. along with shaking for liquefaction and saccharification of starch. Enzymatic hydrolysis was also done for maintaining a control.

The extent of the starch hydrolysis were checked by estimating the glucose produced using DNS (Dinitro Salicylic acid) method [7].

The fermentation process was carried out at stationary condition at 30±2°C in 250ml Bellco fermenter containing 150ml of the medium under anaerobic condition.

Alcohol produced was estimated by distillation process [8-11] and by A.O.A.C [12] . method. An average of 3 sets were taken for calculation and yield was calculated on dry basis.

V. Optimization of temperature for alcohol production

Fermentation was carried out at 26±2°C, 30±2°C and 35±2°C temperatures with a pH of 4.5. Alcohol produced was estimated in each case.


Table 1 represents the production of glucose by hydrolysis in different methods. From the result it is clear that enzymatic hydrolysis(34%) gave better result than acid hydrolysis (21.6%).So, enzymatic hydrolysis by diastase was considered for further research work.

Table 2 represents production of glucose and alcohol by enzymatic hydrolysis for different variety of potato. It was observed that maximum yield of alcohol was obtained from high grade Kufri Jyoti potato(i.e. 74.23%).

Table 3 represent the effect of fermentation temperature on production of alcohol high grade Kufri Jyoti potato at pH 4.5. From the result it is clear that at 30±2°C the alcohol yield(69.56%) was maximum after 48 hrs. of fermentation.


Enzymatic hydrolysis of peeled potatoes especially, high grade Kufri Jyoti variety can be utilized for production of alcohol(ethanol) by Saccharomyces cerevisiae.


Author highly acknowledges the moral support provided by Yobe State University, Nigeria in the present research work.


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Potentials of Potato Starch for Biofuel Production. Fermentative Production of Alcohol by Saccharomyces Cerevisiae utilizing Potato Starch
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potato starch, biofuel, biofuel production, alcohol
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Debajyoti Bose (Author), 2014, Potentials of Potato Starch for Biofuel Production. Fermentative Production of Alcohol by Saccharomyces Cerevisiae utilizing Potato Starch, Munich, GRIN Verlag, https://www.grin.com/document/341834


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