Production of Bioethanol from Cassava Using a Hybrid of Saccharomyces Cerevisiae and Saccharomyces Paradoxus

ABSTRACT  Cassava  is  considered  as  a  potential  source  for  the  commercial  production  of  bioethanol because of its availability and low market price. It can be used as a basic source to support large-scale biological  production of  bioethanol using  microbial amylases. With  the progression  and advancement in enzymology, starch liquefying and saccharifying enzymes are preferred for the conversion  of  complex  starch  polymer  into  various  valuable  metabolites.  These  hydrolytic enzymes can selectively cleave the internal linkages of starch molecule to produce free glucose which can  be utilized  to produce bioethanol  by microbial  fermentation. Ethanol  is  an alcohol with the general formula C2H2n+1OH which can either be produced by manufacture from ethane using steam(the  synthetic route),  production  from biomass  waste using bacteria  or production from sugars and starches by fermentation using yeast. Principally, this project work investigates the  potential  for  the  utilization  of  cassava  as  feed  stock  for  the  production  of  bioethanol  by hydrolyzing  with  enzymes  malted  from  sorghum  grain.  The  hydrolysate  was  then  fermented anaerobically  using  a  hybrid  of  Saccharomyces  cerevisiae  and  Saccharomyces  paradoxus followed by distillation of the bioethanol produce to obtain a high graded ethanol. A process involving the use of cassava feedstock as substrate and sorghum malt as enzymes is presented in this report. After a delayed fermentation period of about 30 days, the end product bioethanol  was  recovered  by  simple  distillation  using  a  oil  bath,  the  fermentation  process resulted in the ethanol yield of 0.250L from a totaling starch content of 301 g, leading to a 77% conversion rate of ethanol produced per gramme of starch consumed. The ethanol produced was found to contain about 18 wt% purity using the specific gravity to ethanol chart as shown in the appendix section of this report.
TABLE OF CONTENTS                         Page Title Page……………………………………………………………………………………i Letter of transmittal…………………………………………………………………………ii Certification…………………………………………………………………………………iii Dedication…………………………………………………………………………………..iv Acknowledgement…………………………………………………………………………..v Table of contents…………………………………………………………………………….vi List of figures………………………………………………………………………………..x List of tables…………………………………………………………………………………xi Abstract……………………………………………………………………………………...xii  CHAPTER ONE:  INTRODUCTION…………………………………………………1  1.1  Background of Proposed Study……………………………………………………. 1    1.2  Aim and Objectives…………………………………………………………………3  1.3  Significance of Study ………………………………………………………………4  1.4  Research Scope……………………………………………………………………..4  1.5  Justification of Study……………………………………………………………….4    1.6  Organization of Study………………………………………………………………4  
CHAPTER TWO:  LITERATURE REVIEW…………………………………………5  2.1  Cassava……………………………………………………………………………..5    2.1.1  History of Cassava…………………………………………………………..5    2.1.2  Cultivation of Cassava………………………………………………………5      2.1.3  Characterization of Cassava…………………………………………………8    2.1.4  Cassava starch content………………………………………………………9  2.1.5  Hydrolysis of Cassava………………………………………………………13      2.1.6  Application of Cassava……………………………...……………………...14  2.2  Yeast…………………………………………………..…………………………...15    2.2.1  Preservation of Yeast Culture…………………..…………………………..15    2.2.2  Saccharomyces cerevisiae……………………..……………………………23      2.2.3  Saccharomyces paradoxus………………………..………………………...24    2.2.4  Mechanism of Yeast Fermentation……………………..…………………..24    2.2.5  Kinetics of Yeast Growth…………………………………..……………….25  2.3  Bioethanol……………………………………………………………..……………27    2.3.1  General Overview…………………………………………..……………….27    2.3.2  Upstream processing in Bioethanol production.............................................28   2.3.3  Feedstock for Bioethanol Production…………………………..……………33.     2.3.4  Advantages and Disadvantages of Bioethanol……………………..……………35    2.3.5  Economic and Environmental Impacts of Bioethanol……………………….37  2.4  Bioethanol from Cassava………………………………….………………………..38  2.4.1  Conventional method of bioethanol production………………………………38  2.4.2  Simultaneous Saccharification and Fermentation (SSF)……………….……..41  2.4.3  Simultaneous Liquefaction Saccharification and Fermentation (SLSF)………41
 CHAPTER THREE: METHODOLOGY……………………………….………………….43  3.1  Introduction……………………………………………………………………………43  3.2  Materials and Reagents………………………………………………………………..43  3.3  Apparatus ……………………………………………………………………………..43  3.4  Description of Apparatus……………………………………………………………...44  3.5  Experimental Procedures………………………………………………………………46    3.5.1  Malting of Sorghum Grain…………………………………………………….46  3.5.2  Cassava Feedstock Preparation/Starch Extraction…………………………….48  3.5.3  Starch Hydrolysis with Sorghum Malt………………………………………..50  3.5.4  Preparation of Organism and Inoculums……………………………………...50   3.5.5  Fermentation of the Hydrolysate……………………………………………...51  3.5.6  Distillation……………………………………………………………………..51   3.5.7  Ethanol Concentration…………………………………………………………52  
CHAPTER FOUR:  RESULTS AND DISCUSSION……………………………………..53   4.1  Results………………………………………………………………………………...53  4.2  Discussion of Results………………………………………………………………….61 
CHAPTER FIVE:  CONCLUSION AND RECOMMENDATION…………………….63  5.1  Conclusion…………………………………………………………………………….63  5.2  Recommendations……………………………………………………………………..64 REFERENCES……………………………………………………………………………….65 APPENDICES………………………………………………………………………………...72