انتاج الايثانول الحيوي من نفايات البطاطا


 
      

Al-Khwarizmi 

Engineering   

Journal 
Al-Khwarizmi Engineering Journal, Vol. 10, No. 3, P.P. 62- 67 (2014) 

 

 

Production of Bioethanol from Waste Potatoes 

 
Alaa Kareem Mohammed*              Safaa Abdalrassol Ali**   

  Jameel Hadi Jiyad*** 
* Department of Biochemical Engineering/ Al-Khawarizmi College of Engineering/ University of Baghdad 
**,***Genetic Engineering and Biotechnology Institute for Postgraduate Studies / University of Baghdad  

@.comalaa_univ: mail-E* 

**E-mail: safaamu2003@yahoo.com 

***E-mail: jammellhadww@yahoo.com 

 
(Received 16 December  2013; accepted 15 June  2014) 

 
 

 

Abstract 

 
In this research, production of ethanol from waste potatoes fermentation was studied using Saccharmyses cerevisiae. 

Potato Flour was prepared from potato tubers after cooking and drying at 85°C. Homogenous slurry of potato flour was 

prepared in water at solid liquid ratio 1:10. Liquefaction of potato flour slurry with α-amylase at 80°C for 40 min 

followed by saccharification with glucoamylase at 65°C for 2 hr .Fermentation of hydrolysate with Saccharomyces 

cerevisiae at 35°C for two days resulted in production of 33 g/l ethanol.  

      The parameters studied were; temperature, time of fermentation and pH. It was found that Saccharification process 

is affected by enzyme Amylo 300 concentration and concentration of 1000µl/100ml gives efficient effect of the process. 

The best temperature for fermentation process was found to be about 35
o
C. Also it was noticed that ethanol production 

was increased as time of fermentation increased but after 48 hr further increase in fermentation time did not have 

appreciable effect. Finally, the optimal value of pH for fermentation process was about 5 to 6. 

 

Keywords: Fermentation, Saccharomyces cerevisiae, saccharification, bioethanol. 

 

 

1. Introduction 
 

Bioethanol as an alternative source of energy 

has received special attention world over due to 

depletion of fossil fuels.  From the 18
th
 century to 

the beginning of this century, major discoveries 

about the biology and chemistry of fermentation 

and distillation made it possible to produce 

cheaper ethanol from variety of organic materials 

[1, 2]. 

To produce ethanol from biomass two key 

processes are followed, first the starch or 

hemicelluloses and cellulose portions of the 

biomass are broken down into simple sugars 

through a process called saccharification. Second, 

the sugars are fermented to produce ethanol. [3, 4] 

The sugary substrates available are 

comparatively expensive than molasses but can be 

easily used for ethanol production with some 

modification in the process. On the other hand 

cellulosic materials are cheaper and available in 

plenty but their conversion to ethanol involves 

many steps and is expensive. The starchy 

substrates are promising due to their economic 

viability and availability. Starchy crops like corn, 

barley, wheat, rice and tuber crops viz. potato, 

sweet potatoes are being exploited for the 

production of bioethanol world wide since it is 

rich in starch, which makes it a cheap substrate 

for ethanol production. The problems associated 

with its processing will also be less than in other 

grains. It is also semi-perishable food which can 

be stored for considerable period without 

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 Alaa Kareem Mohammed               Al-Khwarizmi Engineering Journal, Vol. 10, No. 3, P.P. 62- 67 (2014) 
 

63 

 

spoilage. Good quality alcohol can be produced 

from potato which can be used for fuel. The 

purpose of this research was to explore the 

parameters and operating conditions that give the 

best conversion of potato starch into ethanol. [4, 

5, 6]. 

 

 

2. Experimental Work 
 

2.1. Material and Methods 
 

2.1.1. Potato preparation: Waste of potato was 

brought from chips factory and restaurants. 1 kg 

waste potatoes were cooked with two liters water 

in a pressure cooker at 85 
o
C for one hour then it 

dried overnight in oven at 70
o
C and mashed to a 

fine powder (0.3mm). 

 

2.1.2. Preparation of potato slurry: Slurries 

were prepared from potato powder mixed with 

water at ratio (1:20 w/w). The slurry was treated 

with amylase enzyme (obtained by Himedia) 

(1000µl/100ml) at 80 
o
C for 40 min under shaking 

conditions. 

 

2.1.3. Analyses of waste potatoes: Waste of 

potatoes contained 77% moisture, 18.2% starch, 

2.4 % proteins and 0.6% total sugars while the 

respective hydrolysate of potato was 13.2, 70, 

10.8, 1.5 and 4.5%, (Table 1). 
 

Table 1, 

Composition of waste potato and potato hydrolysate 

[6]. 

Component  Composition (%) 

Waste 

potato 

Potato 

hydrolysate 

Moisture 77 13.2 

Starch 18.2 70 

Proteins 2.4 10.8 

Total sugar 0.6 1.5 

Others 1.8 4.5 

 

 

2.1.4. Saccharification of slurry: 
Saccharification of slurry was carried out at 65

o
C 

for 2 hr using Amylo-300 enzyme (obtained by 

Himedia) of concentration (1000 µl/100ml). The 

reaction was monitored by the yield of total 

reducing sugars estimated by dinitrosalicyclic acid 

method [7]. 

 

2.1.5. Effect of enzyme concentration: The 

liquefied potato flour was saccharified with 

different concentrations of Enzyme Amylo-300 

(600, 800, 1000 µl/100ml) at 65°C. The reaction 

was monitored by the yield of total reducing 

sugars which was estimated by dinitrosalicyclic 

acid method [8]. 

 

2.1.6. Yeast culture: A fast fermentation strain of 

Saccharmyses cerevisiae was maintained on yeast 

extract peptone dextrose agar medium containing 

in grams per 100ml ( potato starch 10; peptone 

0.1; malt extract 0.1 ;  yeast extract 0.2; 

magnesium chloride 6 H20  0.1; calcium carbonate 

0.2  ; ammonium phosphate 0.2 ; and ferrous 

sulfate .7H2O 0.001). Yeast cells were grown in 

inoculums medium at 35
o
C for 20 hr under 

shaking condition (100 rpm) and centrifuged at 

8000 rpm for 20 min.  For testing the effect of pH 

on fermentation few drops of 1N HCl or 1N 

NaOH were added to this medium to obtain the 

desired initial pH [8]. 

 

2.1.7. Fermentation of potato's hydrolysate: 
The hydrolysate of potato was inoculated with 

Saccharmyses cerevisiae of 0.8% concentration 

(w/v) at 35
o
C. Ammonium sulphate of 0.2% 

concentration (w/v) was added as source of 

nitrogen. Flasks were incubated at 35°C under 

stationary condition for 96hr and ethanol content 

was measured at an interval of 24 h by gas liquid 

chromatography (GC 8200) using capillary 

column and flame ionization detector. 

 

 

3. Results and Discussion 
 

3.1. Effect of Concentration 

 

Fig.(1) shows that as enzyme concentration 

increased the total reducing sugar was also 

increased and concentration of 1000 µl/100ml 

gave efficient effect in saccharification. This 

behavior is caused by the higher growth rate of 

microorganisms at high values of inoculums 

concentrations which lead to higher rate of 

organic matters degradation in the process. This 

finding is in agreement with that found by Nagoda 

T [9]. 

 



 Alaa Kareem Mohammed               Al-Khwarizmi Engineering Journal, Vol. 10, No. 3, P.P. 62- 67 (2014) 
 

64 

 

  

Fig.(1) Effect of Amylo concentration on saccharification hydrolysate at 65 C.

0

2

4

6

8

10

12

14

16

18

20

0 30 60 90 120 150 180 210 240 270

Time, min

re
d
u
c
in

g
 s

u
g
a
r 

(%
)

conc.=1000µl/100ml

conc.=800µl/100m

conc.=600µl/100m

 
Fig. 1. Effect of Amylo concentration on Saccharification on hydrolysate at 65 

o
C. 

 

      

Fermentation of 30% slurry of potato 

hydrolysate was carried out at different 

temperatures (25, 30,  35, 40 °C) under stationary 

conditions up to 48 hr. Fig.(2)  shows that 

fermentation at 35
o
C gives maximum content of 

ethanol of 32g/l. This is due to the effect of 

temperature on the activity of the microorganisms. 

It is well known that temperature above 40
o
C 

affects the membrane composition of 

microorganisms, e.g. the phospholipids fatty acid 

composition changes with temperature and hence 

affect the enzymatic system of the 

microorganisms [10]. This leads   in turn to 

decreasing the rate of fermentation process. 

  

 
Fig. 2. Effect of temperature on ethanol production (Enzyme Conc. =1000µl/100ml,Time of fermentation = 48 hr, 

pH=5.5). 

 

 

3.2. Effect of Time Fermentation 
 

Fermentation of potato hydrolysate was carried 

out at 35 °C for different time intervals using 

enzyme concentration (1000µl/100ml) of Amylo-

300 containing amyloglucosidase. Fig.(3) shows 

that ethanol production was increased as time of 

fermentation increased from 24 to 48 hr so it 

reached to 32g/liter at 48hr ;however further 

increase in fermentation time did not have 

appreciable effect. This result is in agreement with 

that mentioned by Wang F [11] and Oner[12]. 



 Alaa Kareem Mohammed               Al-Khwarizmi Engineering Journal, Vol. 10, No. 3, P.P. 62- 67 (2014) 
 

65 

 

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10

Et
h

an
o

l p
ro

d
u

ct
io

n
 g

/l

pH

 

0

5

10

15

20

25

30

35

40

45

50

0 24 48 72 96 120

Time, hr

E
th

a
n

o
l 

p
ro

d
u

c
ti

o
n

, 
g

 /
 l

 
 

Fig. 3. Effect of fermentation time on ethanol production (Enzyme Conc.  =1000µl/100ml, Temp =35
o
C, pH =5.5). 

 
 

3.3. Effect of pH 
 

Figure (4) shows that the production of ethanol 

is increased with increasing pH from 3 to 6. The 

optimal production of ethanol was 32g/l which 

occurs at pH 6.After that the production began to 

decrease with increasing pH and reached to 22 g/l 

at pH 8. This behaviors can be interpreted by the 

effect of pH on the activity of α amylo enzyme, 

Since the activity of this enzyme is severely 

effected by the value of pH specially after value 

of pH=6 ]8[. 

  

 

 

 

 

 

 

 

 

 

 
 

 

Fig. 4.  Effect of pH on ethanol production(Enzyme Conc.=1000µl/100ml, Temp.=35
o
C, time of fermentation=48 

hr.) 

 

 

 

 

 

 

 

 

 

 

 



 Alaa Kareem Mohammed               Al-Khwarizmi Engineering Journal, Vol. 10, No. 3, P.P. 62- 67 (2014) 
 

66 

 

4. Conclusions 
 

1. Saccharification process is affected by enzyme 
Amylo 300 concentration and concentration of 

1000µl/100ml gives efficient effect on the 

process. 

2. The best temperature for fermentation of 
potato starch to produce ethanol using 

Saccharmyses cerevisiae is about 35oC. 

3. Ethanol production was increased as time of 
fermentation increased from 24 to 48 hr; 

however further increase in fermentation time 

did not have appreciable effect.   

4. The optimal value of pH for fermentation 
process to produce ethanol production was 

about 6. 

 

 

5. References 
 

[1] Hill, J.; Nelson, E. ; Tilman, D.; Polasky, S. 
and Tiffancy, D. "Environmental, economic 

and energetic costs and benefits of biodiesel 

and ethanol biofuels". Proc.of the Nat. 

Academy of Sci.  USA, 103; 11206-11210  

(2006). 

[2] Grassi, G. "Modern Bioenergy in the 
European Union, Renewable Energy", Appl. 

Environ. Biotechnology.16: 985- 990 (1999). 

[3] Lemmel, S. A.; Heimsch, R. C. and Korus, R. 
A.  "Kinetics of growth and amylase 

production of Saccharomycopsis fibuligera 

on potato processing wastewater".  Appl. 

Environ. Microbiol. 39, 387-393  (1980). 

[4] Cazetta, M. ; Celligoi, M. ; Buzato, J. and 
Searmino, I. "Fermentation of molasses by 

Zymomonas mobilis" : Effects of 

temperature and sugar concentration on 

ethanol production. Biores. Technol. 98:  

2824-2828 (2007). 

[5] Jarl, K. "Production of microbial food from 
low cost starch materials and purification of 

industry's waste starch effluents through the 

Symba yeast process". Food Technol. 23: 

1009-1012  (1996). 

[6] Kobayashi, F.; Sawada, T. and Ushiyama, T." 
Saccharification and alcohol fermentation in 

starch of steam exploded potato". Appl. 

Biochem. Biotechnol. 69: 177-189 (1998). 

[7] Miller, G. L. "Use of dinitrosalicyclic acid 
reagent for determination of reducing sugar". 

Anal. Chem. 31, 426-428(1959). 

[8] Shigechi, H. ; Koh, J.; Fujita, Y. Matsumoto, 
T. "Direct production of ethanol from raw 

corn starch via fermentation by use of a novel 

surface- engineered yeast strain co-displaying 

glucoamylase and alphaamylase". Appl. 

Environ. Microbiol. 70: 5037- 5040 (2004). 

[9] Nagoda, T. W. and Steinkraus, K. H. 
"Influence of the rate of ethanol production 

and accumulation on the viability of 

Saccharomyces cerevisiae in rapid 

fermentation".  Appl. Environ. Microbiol. 31: 

158-162 (1976). 

[10] Chen, H. Xu, J. and ZH, L. "Temperature 
cycling to improve the ethanol production 

with solid state simultaneous saccharification 

and fermentation". Prikl Biokhim Mikrobiol. 

43:65-68 (2007). 

[11] Wang, F. Gao, J. ;Yang, Y. and Xu, P. 
"Optimization of an ethanol production 

medium in very high gravity fermentation". 

Biotechnol. Lett. 29: 233-236 (2007). 

[12] Oner, E.T., Oliver, S.G. and Kirdar, B., 
Production of ethanol from starch by 

respiration deficient recombinant 

Saccharomyces cerevisiae. Appl. and 

Environ. Microbiol., 71:6443-6445 (2005). 

 

 

 
 

 
 

 

 

 

 

 

 

 

 

 

 



  (2014 ) 62- 67، صفحة 3، العدد10دجلة الخوارزمي الهندسية المجلم                                          عالء كريم محمد                     

 

67 

 

 

 

 

 انتاج االيثانول الحيوي من نفايات البطاطا
 

*** جميل هادي جياد**        صفاء عبد الرسول علي*          عالء كريم محمد  
جامعة بغداد/ كلية الهندسة الخوارزمي/ قسم الهندسة الكيميائية االحيائية * 

جامعة بغداد/ معهد الهندسة الوراثية والتقنيات اإلحيائية ***,**  
 alaa_univ@.com: االلكترونيالبريد *

  safaamu2003@yahoo.com :البريد االلكتروني**

  jammellhadww@yahoo.com: البريد االلكتروني***

 

 
 

 الخالصة
 

تزم تحيزير مسزحول البطاطزا كمزا . دراسة انتاج االيثانول من تخمير نفايات  البطاطا باستخدام خميرة الخبز  سكرومايسزس سيرفيسزيا تفي هذا البحث تم

م58وذلك بطبخ درنات البطاطا وتجفيفها عند درجة حرارة 
o
سائل ومعاملة  المهروس مز   -صلب 1:::تحيير مهروس البطاطا في الماء بنسبة كذلك تم و. 

م51انز يم الفززا اميليز  عنززد درجزة حززرارة 
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م 58دقيقززة وبعزدها معاملززة النزاتن مزز  انز يم كلوكززواميلي  عنزد درجززة 01لمزدة 

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تمزت عمليززة التخميززر . لمزدة سززاعتين 

م 58باستخدام خميرة سكرومايسيس سرفيسيا عند درجة 
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وجزد ا  عمليزة تحويزل النازا الزى سزكر تتزاثر و.  (pH)والدالزة الحاميزية,زمزن التخميزر ,درجة الحزرارة: دراستها في هذا البحث هي  تالعوامل التي تم

سزاعة 05وجد ا  تركي  االيثانول ي داد ب يادة زمن التخميزر لحزد كما. مللتر 11:/مايكرولتر 111: وو ا  افيل تركي  لالن يم ه 511بتركي  ان يم االميلو

م 58درجة حرارة لعملية التخمير هي  أفيلوكانت   اإلنتاجيةعلى  تأثيرولم يالحظ بعد هذا ال من اي 
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