THE ROLES OF TRICHODEMA VIRIDE AND SACCHAROMYCES CEREVISIAE IN THE PRODUCTION OF ALCOHOL FROM IPOMOEA BATATAS (SWEET POTATOES).

ABSTRACT

Sweet potato tubers (peeled) were examined for ethanol production and biomass. The sweet potato tubers were grinded and hydrolyzed/Saccharified enzymatically using Trichoderma viride which resulted to a sugar yield of 7.20% brix and was optimized to 21.05% for fermentation to occur. Saccharomyces cerevisiae from palm wine was used to ferment the hydrolysate to produce alcohol. During the fermentation process, records showed that the specific gravity, pH and sugar content reduced. The sugar reduced from 21.05% to 2.13%, the specific gravity reduced from 1.160g/cmᶟ to 1.020g/cmᶟ and the pH reduced from 6.50 to 2.67. The acidity increased from 0.57% to 2.95% and the alcohol content increased from 1.60% to 10.20% v/v. The produced biomass which started as 0.48% after 24hr of fermentation increased and accumulated to 2.03g/l. An assessment of the produced alcohol showed that it had a boiling point of 78.83ᴼC, a specific gravity of 0.791g/cmᶟ and a pH of 3.53. The total alcohol yield was11.86% v/v. The result of the experiment showed that sweet potato is a potential substrate for alcohol production and biomass used as single cell proteins.

TABLE OF CONTENTS

                                                                                                                                             Pages

      Title                                                                                                                                       i

    Certification                                                                                                                           ii

    Dedication                                                                                                                             iii

   Acknowledgements                                                                                                               iv  

   Table of contents                                                                                                                   v-vii

   List of  tables                                                                                                                          viii

   List of figures                                                                                                                         ix

   Abstract                                                                                                                                   x

   Chapter One

1.0                              Introduction                                                                                         1

1.2                              Aim                                                                                                      4

1.3                              Objectives                                                                                            4

   Chapter Two

2.0                              Literature Review                                                                                5

2.1                              Sweet potato                                                                                         5

2.2                              Nutritional Value                                                                                  5

2.3                              Saccharomyces cerevisiae (palm wine yeast)                                      6

2.4                              History of yeasts                                                                                   8

2.5                              Growth and Nutrition of yeast                                                             8

2.6                              Nutritional Supplements                                                                      9

2.7                              Alcohol Tolerance                                                                               9

2.8                              Biomass                                                                                               10

2.9                              Fermentation                                                                                       10

   Chapter Three

3.0                            Materials and Methods                                                                              12                                                                                                                                                           

3.1                            Materials                                                                                                    12

3.2                            Methods                                                                                                     12

3.3                            Production of sweet potato flour                                                                12

3.4                            Production of palm wine yeast                                                                  12

3.5                            Media Preparation                                                                                     13

3.6                            Preparation of Crude Enzyme Extract                                                        13

3.7                            Saccharification of sweet potato flour                                                        13

3.8                             Determination of sugar content of saccharified direct potato flour          14

3.9                             Optimization of sugar content                                                                   14

3.10                           Fermentation for Biomass and Alcohol production                                  15

3.11                           Determination of pH                                                                                 15

3.12                           Determination of Temperature                                                                  16

3.13                           Determination of Total Solid                                                                     16

3.14                           Determination of Specific Gravity                                                            16

3.15                           Determination of Titratable Acidity (TTA)                                              17

3.16                            Measurement of Biomass                                                                       17

3.17                           Determination of Ethanol Contents                                                         18

   Chapter Four

4.0                             Results                                                                                                      19

   Chapter Five

5.0                             Discussion, Conclusion and Recommendation                                    31

5.1                             Discussion                                                                                                31

5.2                             Conclusion                                                                                                33

5.3                              Recommendation                                                                             33

     References                                                                                                                     34

     Appendix

                                              LIST OF TABLES

Title                                                                         Pages

1                    Quality characteristics of sweet potato flour hydrolysate used                        21

                     for alcohol production.

2                 Changes in quality characteristics of fermenting sweet potato flour must          22

                     during the  production of ethanol and biomass.

3                   Quality characteristics of produced alcohol.                                                      23

                                        LIST OF FIGURES  

Title                                                             pages

1                       Changes in pH during fermentation period.                                                 24

2                       Changes in Temperature during fermentation period.                                  25

3                       Titratable acidity during fermentation.                                                         26

4                       Changes in specific gravity during fermentation period.                              27

5                       Changes in sugar content during fermentation period.                                 28

6                       Alcohol content during fermentation period                                                 29

7                       Concentration of Biomass during fermentation period.                                30

   CHAPTER ONE

            1.0        INTRODUCTION

There is a considerable interest in developing bio renewable alternatives to substitute fossil fuels such as bioethanol as transportation fuel. Bioethanol contributes a diminish petroleum dependency, generates new development opportunities in the agricultural and agro industrial sectors and is of environmental benefits. The main feedstock for bioethanol production is the 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 (Duvernay, et al. 2013, Lee, et al. 2012; Srichuwong, et al. 2009; Ziska, et al. 2009). Industrial sweet potatoes are not intended for use as 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 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 (Duvernay, et al. 2013; Ziska, et 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 growth cycle, low illness incidence and plagues, cover rapidly the soil and therefore protect it from the erosive rain and controlling the weed problem (Ann, et al. 2011; Duvernay, et al. 2013; Vilaro, et 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 (Ann, et al. 2011; Shaibani, et al. 2011). High ethanol concentration can be reached in 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 (Shanavas, et al. 2011; Walker, et al. 2002; Yatanabe, 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 assess 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 bioethanol 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 as 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 (Duvernay, et al. 2013; Moorthy, 2002; Srichuwong, et al. 2005) 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 (Duvernay, et 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 an average yield of up to 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 (Yang, et al. 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 dietry fiber, which are important for human health. Sweet potato tops (leaves and stems) contain additional nutritional components in much higher concentrations than 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 other 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 lignocelluloses to alcohol as substrate was reported by (Xang and Zhao 2011).

1.2       AIM

The aim of this research is to utilize sweet potato (Ipomoea batatas) as biomass for alcohol production using Trichoderma viride and Saccharomyces cerevisiae.

1.3      OBJECTIVES

Ø  To saccharify sweet potato (cellulose) using Trichoderma viride.

Ø  To generate biomass and ethanol using Saccharomyces cerevisiae.

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