One fraction of the existent petroleum is not extractable or the difficulties associated to extraction are 
very expensive making them unviable. This situation leads to a decrease in petroleum stocks all over 
the world and a resulting increment on its price, affecting in particular the transportation sector, since 
there is no relevant alternative to fossil petroleum

Duarte, C.

Lima-Costa, Maria Emília

Marques, L.

Raposo, Sara

Sousa, Catarina

Sapientia

Production of Bioethanol from Sweet Potato, Agro-Industrial Wastes   Luís Marques, Catarina Duarte, Sara Raposo, Catarina Tavares, Mª Emília Lima-Costa   Centre for Marine and Environmental Research-CIMA, Eng and Environmental Biotechnology Laboratory, Faculty of Sciences and Technology, University of Algarve, Campus de Gambelas, 8005-139 Faro; mcosta@ualg.pt   Keywords: Bioethanol, Saccharomyces cerevisiae, Sweet Potato, Fermentation  One fraction of the existent petroleum is not extractable or the difficulties associated to extraction are very expensive making them unviable. This situation leads to a decrease in petroleum stocks all over the world and a resulting increment on its price, affecting in particular the transportation sector, since there is no relevant alternative to fossil petroleum. In addition, the recent concern about the environmental deterioration from the over consumption of petroleum derived products, which highly contributes to the greenhouse effect, is threatening the sustainability of the human society. For these reasons, the search for clean and renewable sources is one of the highest challenges of mankind nowadays. Biomass is one of the oldest and the most promising energy sources and includes organic and animal wastes, wastewater, energy crops, agricultural and industrial residues that can be used for the production of biofuels. It can be biologically converted to liquid or gaseous fuels, such as ethanol, methanol, methane and hydrogen [1].  Bioethanol is obtained from plant materials that are produced by photosynthesis, which is a photochemical process that uses atmospheric CO2. When the bioethanol is burned, it liberates CO2 that returns back to the atmosphere, where it came from. It means that the balance between CO2 consumption and liberation is preserved and use of bioethanol as a source of power could partially help to solve the global ecological problems such as the greenhouse effect and global warming [2]. Currently, ethanol is the main biofuel used in the world and its use is being progressively widespread, arising also the need for new and more yielding sources of ethanol and processes of production. Ethanol industry requires sufficient and cheap feedstock in order to reduce the costs of production. To avoid competition with materials conventionally destined to food, ethanol industry should be based on non-grain crops and biomass [3]. In Portugal, region of Algarve, Aljezur is a town with great sweet potato tradition and high output of sweet potato. The sweet potato of Aljezur is the adventitious, fleshy, tuberous root of the plant Ipomoea batatas (L.). Elongated and pear shaped, its skin is purple or reddish brown and the flesh yellow. Saccharomyces cerevisiae, a Crabtree-positive yeast, is capable of growth and ethanol production under both aerobic and anaerobic conditions being extensively used to convert sugars to ethanol for the production of biofuels [4]. The strain used during this work is a high ethanol tolerant strain and allows to attain high yields and productivities.    The aim of this work is to study the fermentative process for production of bioethanol using sweet potato agro-industrial wastes. Soluble sugars were extracted using different experimental procedures. A value of 75.8 g/L in total sugars was achieved, for sweet potato at an optimized ratio of 2:10 (w/v) in aqueous medium, using a heat treatment at 110 ºC for 90 min.  Soluble sugar fermentations were performed in Erlenmeyer flasks, with YEPD medium at 30 ºC and 150 rpm (Figure 1), using extract of sweet potato as carbon source.           Figure 1 – Concentrations (g/L) of ethanol, total sugars and dry weight during fermentation process times (h), with YEPD medium at 30 ºC and 150 rpm.   Maximum ethanol concentration, maximum ethanol productivity and yield after fermentation were respectively 32.9 g/L, 0.89 g/(L.h) and 43 %. These high values were achieved using soluble sugars of sweet potato extracted at mild conditions.   An enzymatic hydrolysis of starch has to be applied in order to increase carbon source availability and consequently the amount of ethanol produced.   References  [1] Antonopoulou G, Gavala H, Skiadas I, Angelopoulos K, Lyberatos G, 2008. Biofuels generation from sweet sorghum: Fermentative hydrogen production and anaerobic digestion of the remaining biomass. Bioresource Technology  99:110-119. [2] Choteborská P, Palmarola-Adrados B, Galbe M, Zacchi G, Melzoch K, Rychtera M, 2004. Processing of wheat bran to sugar solution. Journal of Food Engineering 61:561-565. [3] Zhang K and Feng H, 2010. Fermentation potentials of Zymomonas mobilis and its application in ethanol production from low-cost raw sweet potato. African Journal of Biotechnology Vol 9(37):6122-6128.  [4] de Kock S, du Preez J, Kilian S, 2001. The effect of growth factors on anoxic chemostat cultures of two Saccharomyces cerevisiae strains. Biotehnology Letters 23:957-962. 010203040506070800 10 20 30 40 50 60 70Concentration (g/L)Fermentation time (h)EthanolSugarsDry Weight

Production of bioethanol from sweet potato, agro industrial wastes

Universidade do Algarve

Production of Bioethanol from Sweet Potato, Agro-Industrial Wastes  
 
Luís Marques, Catarina Duarte, Sara Raposo, Catarina Tavares, Mª Emília Lima-Costa  
 
Centre for Marine and Environmental Research-CIMA, Eng and Environmental Biotechnology Laboratory, 
Faculty of Sciences and Technology, University of Algarve, Campus de Gambelas, 8005-139 Faro; 
mcosta@ualg.pt  
 
Keywords: Bioethanol, Saccharomyces cerevisiae, Sweet Potato, Fermentation 
 
One fraction of the existent petroleum is not extractable or the difficulties associated to extraction are 
very expensive making them unviable. This situation leads to a decrease in petroleum stocks all over 
the world and a resulting increment on its price, affecting in particular the transportation sector, since 
there is no relevant alternative to fossil petroleum. 
In addition, the recent concern about the environmental deterioration from the over consumption of 
petroleum derived products, which highly contributes to the greenhouse effect, is threatening the 
sustainability of the human society. For these reasons, the search for clean and renewable sources is 
one of the highest challenges of mankind nowadays. 
Biomass is one of the oldest and the most promising energy sources and includes organic and animal 
wastes, wastewater, energy crops, agricultural and industrial residues that can be used for the 
production of biofuels. It can be biologically converted to liquid or gaseous fuels, such as ethanol, 
methanol, methane and hydrogen [1].  
Bioethanol is obtained from plant materials that are produced by photosynthesis, which is a 
photochemical process that uses atmospheric CO2. When the bioethanol is burned, it liberates CO2 that 
returns back to the atmosphere, where it came from. It means that the balance between CO2 
consumption and liberation is preserved and use of bioethanol as a source of power could partially 
help to solve the global ecological problems such as the greenhouse effect and global warming [2]. 
Currently, ethanol is the main biofuel used in the world and its use is being progressively widespread, 
arising also the need for new and more yielding sources of ethanol and processes of production. 
Ethanol industry requires sufficient and cheap feedstock in order to reduce the costs of production. To 
avoid competition with materials conventionally destined to food, ethanol industry should be based on 
non-grain crops and biomass [3]. 
In Portugal, region of Algarve, Aljezur is a town with great sweet potato tradition and high output of 
sweet potato. The sweet potato of Aljezur is the adventitious, fleshy, tuberous root of the plant 
Ipomoea batatas (L.). Elongated and pear shaped, its skin is purple or reddish brown and the flesh 
yellow. 
Saccharomyces cerevisiae, a Crabtree-positive yeast, is capable of growth and ethanol production 
under both aerobic and anaerobic conditions being extensively used to convert sugars to ethanol for 
the production of biofuels [4]. The strain used during this work is a high ethanol tolerant strain and 
allows to attain high yields and productivities.    
The aim of this work is to study the fermentative process for production of bioethanol using sweet 
potato agro-industrial wastes. Soluble sugars were extracted using different experimental procedures. 
A value of 75.8 g/L in total sugars was achieved, for sweet potato at an optimized ratio of 2:10 (w/v) 
in aqueous medium, using a heat treatment at 110 ºC for 90 min.  
Soluble sugar fermentations were performed in Erlenmeyer flasks, with YEPD medium at 30 ºC and 
150 rpm (Figure 1), using extract of sweet potato as carbon source. 
 
 
 
 
 
 
 
  
 
Figure 1 – Concentrations (g/L) of ethanol, total sugars and dry weight during fermentation process times (h), 
with YEPD medium at 30 ºC and 150 rpm. 
 
 
Maximum ethanol concentration, maximum ethanol productivity and yield after fermentation were 
respectively 32.9 g/L, 0.89 g/(L.h) and 43 %. These high values were achieved using soluble sugars of 
sweet potato extracted at mild conditions.   
An enzymatic hydrolysis of starch has to be applied in order to increase carbon source availability and 
consequently the amount of ethanol produced. 
 
 
References 
 
[1] Antonopoulou G, Gavala H, Skiadas I, Angelopoulos K, Lyberatos G, 2008. Biofuels generation 
from sweet sorghum: Fermentative hydrogen production and anaerobic digestion of the remaining 
biomass. Bioresource Technology  99:110-119. 
[2] Choteborská P, Palmarola-Adrados B, Galbe M, Zacchi G, Melzoch K, Rychtera M, 2004. 
Processing of wheat bran to sugar solution. Journal of Food Engineering 61:561-565. 
[3] Zhang K and Feng H, 2010. Fermentation potentials of Zymomonas mobilis and its application in 
ethanol production from low-cost raw sweet potato. African Journal of Biotechnology Vol 9(37):6122-
6128.  
[4] de Kock S, du Preez J, Kilian S, 2001. The effect of growth factors on anoxic chemostat cultures of 
two Saccharomyces cerevisiae strains. Biotehnology Letters 23:957-962. 
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50 60 70
C
o
n
ce
n
tr
at
io
n
 (
g/
L)
Fermentation time (h)
Ethanol
Sugars
Dry Weight


https://sapientia.ualg.pt/bitstream/10400.1/4819/1/Production%20of%20Bioethanol%20from%20Sweet%20Potato%2c%20Agro-Industrial%20Wastes.pdf

Production of bioethanol from sweet potato, agro industrial wastes

Abstract

Similar works

Full text

Available Versions

Sapientia

Universidade do Algarve