ABSTRACT
Sweet potato tubers (peeled) were examined for ethanol production and biomass. The sweet potato tubers were grinded and hydrolysed/saccharified enzymatically using Trichoderma viride which resulted to a sugar yield of 7.2%brix and was optimized to 22.4% for fermentation to occur.Sacccharomycescerevisae from palm wine was used to ferment the hydrolysate to produce alcohol. During the fermentation process, records shows that the specific gravity,pH and sugar content reduced.The sugar reduced from 12.4% to 1.64%,The specific gravity reduced from 1.127g/cm3 to 1.016g/cm3 and the pH reduced from 6.0 to 3.1.The acidity increased from 0.24% to 1.53% and the alcohol content increased from 1.16% to 11.86%V/V.The produced biomass which started as 0.16% after 24h of fermentation increased and accumulated to 1.97g/l. An assessment of the produced alcohol showed that it had a boiling point of 78.830C,a specific gravity of 0.791g/cm3 and a pH of 3.53.The total alcohol yield was 11.86%V/V.The result of the experiment shows that sweet potato is a potential substrate for alcohol production and biomass used as single cell proteins.
Table of Contents
i
Certification ii
Dedication iii
Acknowledgement iv
Table of Contents v
List of Tables vii
Figures of Tables viii
Abstract ix
CHAPTER ONE
1.0 Introduction 1
1.2 Aim 4
1.3 Objectives 4
CHAPTER TWO
2.0 LITERATURE
REVIEW
2.1 Sweet Potato 5
2.2 Nutritional Value 6
2.3 Saccharomyces
cervisiae (Palm wine yeast) 7
2.4 History of
Yeasts 8
2.5 Growth and Nutrition of Yeast 9
2.6 Nutritional Supplements 9
2.7 Alcohol Tolerance 10
2.8 Biomass 11
2.9 Fermentation 11
CHAPTER THREE
3.0 MATERIALS
& METHODS
3.1 Sources of
Materials 13
3.2 Sweet Potato Processing 13
3.3 Sampling and Sample Preparation 13
3.4 Media Preparation 13
3.5 Isolation of palm wine yeast 14
3.6 Hydrolysis of Sweet Potato with Trichodermaviride (Saccharification) 15
3.7 Determination of pH 15
3.8 Determination of Titratable Acidity 16
3.9 Determination of Specific Gravity 16
3.10 Determination of Sugar 17
3.11 Determination of Biomass 18
3.12 Alcohol Distillation 19
CHAPTER FOUR
4.0 RESULTS
CHAPTER FIVE
5.0 DISCUSSION,
CONCLUSION AND RECOMMENDATION
5.1 Discussion 26
5.2 Conclusion 27
5.3 Recommendation 28
References
LIST OF TABLES
Table Title Page
1 Quality
characteristics of sweet potato flour hydrolysate used 20
for
alcohol production.
2 Changes in quality
characteristics of fermenting sweet potato
21
must
during alcohol and Biomass production.
3 Quality characteristics of
produced alcohol. 22
LIST OF FIGURES
Figure Title Page
1: Change in
PH during fermentation period 23
2: Titratable
acidity during fermentation 24
3: Change in
Temperature during fermentation period 25
4:
Concentration of Biomass during Fermentation Period 26
5: Change
in Specific gravity during fermentation period 27
6: Alcohol
content during fermentation period 28
7: Change
in Sugar content during fermentation period 29
CHAPTER ONE
1.0
Introduction
There is a considerable
interest in developing bio renewable alternatives to substitute fossil fuels
such as bio ethanol as transportation fuel. Bio ethanol contributes a diminish
petroleum dependency, generates new development opportunities in the
agricultural and agro industrial sectors more farm work and environmental benefits.
The main feedstock for bioethanol production are sugarcane and corn grain.
Sweet potato (Ipomoea batatas) has been considered a
promising substrata for alcohol fermentation since it has a higher starch field
per unit land cultivated than grains (Duvernayet al., 2013, lee et al.
2012; Srichuwonget al., 2009; Zisikaet al., 2009). Industrial sweet potatoes
are not intended for use as a food crop. They are bred to increase its starch
content, significantly reducing its attractiveness as a food crop when compared
to other conventional food cultivars (visual aspect, color, taste). Therefore,
they offer potentially greater fermentable sugar yields from a sweet potato
crop for industrial conversion processes and the opportunity to industrial
conversion processes and the opportunity to increase planted acreage (even on
marginal lands beyond what is in place for food. It has been reported that some
industrial sweet potatoes breeding lines developed could produce ethanol yield
of 4500 – 6500L /ha compared to 2800 – 3800L /ha for corn (Duvernayet al., 2013; Ziskaet al., 2009). Sweet potato has several agronomic characteristics
that determine its wide adaptation to marginal lands such as drought resistant,
high multiplication rate and low degeneration of the propagation material,
short grow cycle, low illness incidence and plagues, cover rapidly the soil and
therefore protect it from the erosive rains and controlling the weed problem (Cao
et al.,2011; Duvernayet al., 2013; Vilaroet al., 2009). Previous transformation of the raw material into
chips or flour (powder) can be done in order to facilitate its transport and /
or plant conservation. An effective ethanol production process is one where the
amount of water added is minimal since more energy will be required to remove
it at the end of the process if the final ethanol concentration is low (Cao et al., 2011; Shenet al., 2011). High ethanol concentration can be reached if the
fermentable sugar concentration. In the case of ethanol production from root
and tuber crops, it implies the use of a very high gravity (VHG) medium with
high solid content and high viscosity. The high viscous nature causes several
handling difficulties during process, and may lead to incomplete hydrolysis of
starch to fermentable sugars (Shanavaset.
al., 2011; Wang et al., 2008; Watanabe
et al., 2010; Zhang et al. 2011).
Fresh sweet potato
contains high water content. The drying process of this material is an aspect
to be studied to optimize its transport, storing and processing. The use of
flour of sweet potato would allow working with higher sugar concentration
during the fermentation than fresh sweet potato without the addition of water.
In this case, it should be assessed the energy saving of manipulating lesser
amount of material, the handling of high viscous material, the extra cost of
drying and the effect of drying on the performance of the process (Conversion
of starch of fermentable sugars) (Moorthy 2002).
The conventional process
for bio ethanol production from starch based materials includes the conversion
of starch into fermentable sugars which generally takes place in two enzymatic
steps: liquefaction using thermal-stable, alpha amylase and saccharification by
addition of amyloglucosidase (AMG). Most studies of Starch hydrolysis use
enzymes, temperature conditions and reaction times which have been done for
grains, such corn. The starch of sweet potatoes is considered more complex than
cereal starches, making it more challenging to hydrolyze into fermentable
sugars. Besides, the digestibility of starch by enzymes vaines among different
cultivars (Auvernayet al., 2013;
Moorthy 2002; Srichuwonget al., 2008)
yet there is still a need to establish a more defined biologically based
approach to sweet potato starch conversion and evaluate the enzymes and
processing conditions suitable for effective fermentable sugar production
(Duvernayet al., 2013). The sweet
potatoes used in the article has biomass yields of 10t /ha (dry basis), higher
value than cultivated varieties for human consumption which presented as
average yield of up 4.2t /ha.
Sweet potato roots are
bulky and perishable unless cured. This limits the distance over which sweet
potato can be transported economically. It was established that in cases where
countries are capable of generating surplus, it tends to be relatively
localized but dispersed and this leads to lack of market integration and limits
market size (Katan and De Roos, 2007; FAO, 2011). Moreover, production is
highly seasonal in most countries leading to market variation in the quantity
and quality of roots in markets and associated price swings.
Sweet potato consumption
has been adjudged to decline as incomes rise – a change often linked with
urbanization, partly because of the lacks of post-harvest processing or storage
(FAOSTAT, 2008;Centro internacional de ia papa, 2009). The latter can lengthen
the period for which sweet potato can be marketed but may also be relevant for
subsistence oriented households to increase the period over which sweet potato
can be consumed, particularly where there is a market dry season. A sensible
approach to achieve the goal of sweet potato product development would be to
increase the nutritional content of this highly consumed crop.
Sweet potato is one of
the crops selected by the U.S National Aeronautics and space administration
(NASA) to be grown in a controlled ecological life support system as a primary
food source. Recent studies show that sweet potato contains such functional
components as polyphenols, anthocyanins and dietary fiber, which are important
for human health. Sweet potato tops (leaves and stems) contain additional
nutritional components in much higher concentrations that in many other
commercial vegetables. Sweet potato leaves are cooked as a vegetable in many
parts of the world. They are rich in vitamin B, β – carotene, iron, calcium,
zinc and protein, and the crop is more tolerant of disease, pests and high
moisture than many others leafy vegetables grown in the tropics. Because sweet
potato tops can be harvested several times a year their annual yield is much
higher than many other green vegetable.
Currently there is a
growing interest for ecological sustainable bio-fuels all over the world. In
Nigeria, simultaneous Saccharification and fermentation of lignocellulose to
alcohol as substrate was reported by (Park andBarrtti 1995).
1.2 AIM
The aim of this research
is to utilize sweet potato(ipomoea batatas) as Biomass for Alcohol production
usingTrichodermaviride and Saccharomyces cerevisae.
1.3 OBJECTIVE
- To saccharify sweet
potato (cellulose) using Trichodermaviride
- To
generate biomass and ethanol using Saccharomyces
cerevisae.
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