SACCHARIFICATION OF SOURSOP PEEL FOR ETHANOL PRODUCTION

ABSTRACT

This work critically analyses the saccharification of soursop peel for ethanol production. The increasing demand for ethanol production for various industrial purposes has necessitated increased production of this ethanol using lignocellulose biomass. Lignocellulose biomass is very rich and abundant source of energy and in the process of reducing the cost of ethanol production, lignocellulose biomass is now of interest due to its abundant availability. Aspergillus niger with its high enzymatic activity was used to hydrolyse the pretreated soursop peels. After hydrolysis, Saccharomyces cerevisiae were inoculated into the hydrolysates separately at room temperature to ferment for 11 days. During fermentation period, changes in the quality parameters of pH, temperature, titrateable acidity, total solid, specific gravity, sugar contents and alcohol yield were monitored. The temperature fluctuated between 290C and 300C with pH decreasing from 6.20 to 2.40. The sugar content reduced from 21.01% to 2.23% alcohol contents increased to a maximum of 9.86%. The work reveals that soursop peel is a good substrate for bioethanol production regarding to its 9.86% yield of ethanol after saccharification. 

TABLE OF CONTENTS

Certification                                                                                                                           i

Dedication                                                                                                                              ii

Acknowledgment                                                                                                                   iii

Table of Contents                                                                                                                   iv

List of tables                                                                                                                           viii

Abstract                                                                                                                                  ix

CHAPTER ONE

1.0           INTRODUCTION                                                                                                   1

1.1       Saccharomyces cerevisiae                                                                                        6

1.2       Aims                                                                                                                           7

1.3       Objective                                                                                                                    7

CHAPTER TWO

2.0           LITERATURE REVIEW                                                                                      8

2.1       Soursop                                                                                                                      8

2.2       Nutrient Composition of Soursop                                                                           12

2.2.1    Lignocellulosic Biomass                                                                                           14

2.2.2    Second Generation Feedstock                                                                                  14

2.2.4    Hydrolysis and Fermentation Of Lignocellulosic Biomass                                    15

2.3       Bioethanol                                                                                                                 16

2.3.1    Production and Utilization of Ethanol in Nigeria                                                    18

2.4       Microorganisms of Interest in this Research Work                                                20

2.4.1    Aspergillus niger                                                                                                       19

2.4.2 Saccharomyces cerevisiae                                                                                       20

CHAPTER THREE

MATERIALS AND METHODS

3.1       Study Area                                                                                                                 21

3.2       Source of Materials                                                                                                   21

3.3       Micro-Organisms                                                                                                       21

3.3.1    Sample Preparation (pre-treatment)                                                                         21

3.3.2    Preparation of Fungi Inoculums Aspergillus niger.                                    23

3.4           Preparation of Yeast Inoculums (Palm wine Yeast)                                               22

3.5       Media Preparation                                                                                                     22

3.6       Deliquification of substrate                                                                                      23

3.7       Optimization of Hydrolysate                                                                                    23

3.8       Saccharification for bioconversion to produce ethanol                                          24

3.9       Method of Analysis                                                                                                   24

3..9.1   Determination of pH                                                                                                 24

3.9.2    Determination of Temperature                                                                                 25

3.9.3    Determination of Specific Gravity.                                                                          25

3.9.4    Determination of Total Solids                                                                                  26

3.9.5    Determination of Titratable Acidity (TTA)                                                             26

3.9.6    Determination of Sugar Content.                                                                             27

3.9.7    Determination of Ethanol Content                                                                           28

3.9.8    Statistical Analysis                                                                                                    28

CHAPTER FOUR

4.1       RESULT                                                                                                                   29

CHAPTER FIVE

DISCUSSION, CONCLUSION AND RECOMMENDATION                                   

5.1       Discussion                                                                                                                 31

5.2       Conclusion                                                                                                                 32

5.3       Recommendation                                                                                                      32

            Reference                                                                                                                   33

            Appendices                                                                                                                40

LIST OF TABLES

Table 4.1        Changes in quality parameters of fermenting sousop peels using saccharomyces cerevisiae                       30

SECTION ONE

1.0     INTRODUCTION

Consumers from food borne illness have become a global challenge. Food borne disease covers a wide range of illness and is triggered by agents that were consumed along with food. The increase in foodborne illness outbreaks raises food safety concerns. According to World Health Organization (WHO), the contamination of food may occur at any stage in the process from food production to consumption (“farm to fork”) and can result from environmental contamination, including the pollution of water, soil, air (WHO, 2007).

The centers for disease control and prevention (CDC) has stated that foodborne diseases cause approximately 1000 reported disease outbreaks (CDC, 2011). They are considered an emergent public health problem in both developed and developing countries (WHO, 2007). The attachment of bacteria with subsequent development of biofilms in food processing environments is a potential source of contamination that may lead to food spoilage or transmission of disease. The surface of equipment used for food handling, storage or processing are recognized as major sources of microbial contamination. Biofilms are frequent source for infections (Consterton et al., 1999). Biofilms are a consortium or aggregation of microorganisms and extracellular substances in association with a solid surface in contact with liquid. It is nature of microorganism to attach to wet surfaces, and form slimy layer composed of extracellular DNA, Proteins, polysaccharides which are the major components of extracellular polymeric substances (EPS) which help to protect themselves from grazers and harsh environment. Biofilms can be beneficial or detrimental to the environment on which they form.  For example, stream biofilm is capable of recycling organic matter.

Biofilms forming on food contact surfaces can lead to hygienic problems and economical losses due to food spoilage. Bacteria irreversibly attach to the surfaces and produce EPS, which helps bind cells together, to the surface, and other particulate materials.

Cells also communicate between themselves to initiate antibiotic biosynthesis, and extracellular enzyme biosynthesis. These organisms may survive for prolonged periods, depending on the amount and nature of residual soil, temperature, and relative humidity. Since they can render their inhabitants more resistant to disinfectant (Bower et al., 1996; Sidhu et al., 2001), biofilms have become problematic in wide range of food industries, including brewing (Fleming and Ridway, 2009), seafood processing (Shikongo-Nambabi, 2011), dairy processing (Chmielewski and Frank, 2003), poultry processing (Harvey et al., 2007) and meat processing (Sofos and Geornara, 2010). Areas that are more prone to biofilm development include dead ends, joints, valves and gaskets. Pits and cracks may also develop in which soil and bacteria can collect. Much review has been discussed to gain deeper understanding of biofilms and identify a solution in order to avoid contamination of food stuffs. This seminar explains the problem of biofilms in food industries and the current and innovational control strategies that have been used to combat the challenges caused by biofilms.

1.1       Physical Environment

Physical properties of the environment are essential for microorganism attachment to the substratum, biofilm formation, and microbial processes. For example, food conditioning surfaces may promote the attachment of bacteria. The pH and temperature also affect microbial metabolism processes. Some of the physical conditions are described below.

1.1.1    Conditioning of a Surface

Biofilm formation can occur on any submerged surfaces in any environment with the present of bacteria. On food preparation surfaces, bacteria, inorganic and organic materials get adsorb on the surface in minutes of substratum immersion into liquids leading to conditioning surfaces. In food industry, this conditioning film may be proteins from milk or meat. Protein from milk was studied to adsorb to numbers of food-contacting surfaces such as Teflon, stainless steel, and aluminosilicate (Zottola and Sasahara, 1994). The conditioning can alter physio-chemical properties of the surface, surface charge, surface free energy, surface hydrophobicity, which further results in bacterial attachment on the surface (Kumar and Anand,1998).

1.1.2    Surface Charge and Hydrophobicity

Surface charge and hydrophobicity of both bacterial cells and a conditioning surface play an important role in microbial attachment on the surface. These two factors have an impact on the length of time cells are associated with the substratrum. Surface charge results in electrostatic interaction between 2 surfaces. Moreover, cell surface hydrophobicity is also important in adhesion because hydrophobic interaction tends to increase with increasing non-polar property of each surface.

1.1.3    Surface Topography

The relationship between surface roughness and the attachment and growth of bacteria may vary. It was shown that two strains of Yersinia have a strong correlation between the roughness amplitude of the substratrum and adhesion. On the other hand, another showed that little correlation was found on attachment of streptococci to stainless steel.

1.1.4    pH and Temperature

The pH and temperature of a contact surface govern many physical and biological processes of bacterial cells. It was studied that the maximum adhesion of Pseudomonas fragi to stainless steel surfaces was at the pH range of 7 to 8, which was also optimum for cell metabolism. Another study showed that Yersinia enterocolitica attached to stainless steel surfaces better at 21 °C than at 35 °C or 10 °C.

1.1.5    Oxygen Availability and Moisture

The structure of biofilms has a porous structure with a number of capillary water channel within which water and nutrients are transported through. It is believed that these capillaries are responsible for oxygen transport to the inner areas of biofilms. Unfortunately, due to oxygen limited diffusion ability and oxygen consumption, the inner areas encounter low oxygen concentration or anaerobic condition. This phenomenon explains why aerobic and anaerobic bacteria can live together in biofilms.

1.1.6    Stainless Steel as a Food Source Contact Surface

Stainless steel is the most common food contact surface used in the food industry. Stainless steel is suitable for the food industry because of the stability of physical and chemical properties at a various processing temperature. It is highly resistant to corrosion and easy to clean. However, if taking a look at microscopic level of stainless steel surface, it is amazing that stainless steel is composed of cracks and crevices. These structures are different from macroscopic appearance. Such topography allows bacteria and organic substances from food to attach. Studies have shown the attachment of food-borne pathogens and spoiled microorganisms to stainless steel.

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