Optimizing Saccharification of Cellulosic Waste Using Trichoderma viride

Abstract

Cellulose is one of the major components of municipal solid waste. When cellulosic waste is burnt, as has been the norm, a great deal of air pollution occurs, and human health is at risk. To curb such negative effects, saccharification of cellulosic waste has been lauded as a sustainable alternative. This converts cellulosic waste into useful bio-products. The main issue with saccharification is the rate of reaction which can be hastened or slowed down by varying certain conditions under which the reaction takes place, including alkalinity and temperature. In this research, saccharification of cellulosic waste is conducted using the fungus Trichoderma viride. The optimal conditions for the reaction are then investigated by varying the temperature and alkalinity. For students seeking biomedical science dissertation help, getting the accessibility to explore innovative approaches like how saccharification can be presented in research happening in the field.

Chapter 1

Introduction

Waste separation is the process by which waste is sorted out into different elements. For any city, there are many different forms of waste as well as waste categorization [1]. The following are the most common forms of waste regularly produced in the cities: biomedical/clinical waste, chemical waste, agricultural waste, animal by-products, commercial waste, construction and demolition waste, domestic waste, electronic waste, food waste, green waste, hazardous waste, organic waste, packaging waste, radioactive waste, retail hazardous waste, sharps waste, and slaughterhouse waste.

Separation of waste is important for the protection of the environment [2]. It is estimated that about 40 - 60 % of municipal solid wastes is rich in cellulose. Cellulose is also abundant in wastes from forest products, agriculture, and fruit vegetable processing. The general approach has been to burn such wastes so as to clear farmlands for the next planting season. Exposure to the high concentrations of air pollutants produced when burning such wastes has been proven to be harmful to human health [3]. Some of the short term effects include burning of the eyes, nose, and throat, breathing difficulties, vomiting, and headaches. Long term effects include respiratory diseases such as asthma and bronchitis. The resultant smoke has also been shown to contain carcinogenic substances, as well as particulate matter that can harm a person’s cardiac, hormonal, and immune system. As such, the practice of burning agricultural waste should be abandoned because of such negative effects. A good alternative to burning is recycling these wastes into useful products.

The cellulose content in wastes can be converted to simpler sugars through the process of saccharification. This is possible with the help of the fungus Trichoderma viride [5]. The end product of the saccharification process is glucose syrup. This is an important raw material for single cell protein production and also a source of fermentation chemicals. However, the saccharification reaction can prove problematic due to the fact that cellulose is both insoluble and crystalline. The surface area of cellulose exposed is a great determinant of the reaction rate [6]. Also, many cellulosic wastes contain lignin which may limit the access of the enzyme to the cellulose. Some of the methods used to increase the reaction rate include phosphoric acid swelling, alkali swelling, acid pretreatment, lignin removal, and irradiation. The level of alkalinity affects the reaction rate as well. It is worthwhile to investigate the optimum amounts of these substances needed to make the reaction rate as high as possible.

Statement of the Problem

Saccharification of cellulosic waste is a more sustainable approach to dealing with waste as compared to burning [5]. However, the reaction rate for the saccharification process may prove to be very slow because it involves the breakdown of cellulose into simpler sugars. Cellulose has a compact structure that results from its tight bonding and crystallinity. This makes it difficult to be used by enzymes in chemical reactions. To hasten the reaction rate, an optimum environment must be provided. The main factors that affect the reaction rate of the saccharification process include alkalinity, temperature, and degree of crystallinity of the cellulose. This research aims at investigating the optimal conditions for the saccharification process.

Research aims and objectives

The main aim of this research is to investigate the optimal conditions for the saccharification of cellulosic waste. This will be achieved by consideration of the following specific objectives:

1. Determining the optimum temperature for the saccharification reaction.

2. Determining the optimum alkalinity for the saccharification reaction of cellulosic waste.

3. Determining the optimum degree of crystallinity for the saccharification process.

Thesis Structure

This thesis consists of 3 chapters, a list of references and appendices.

Chapter 1 presents a summarized statement of the research topic and the importance of the research. It digs deeper into why this specific research topic was chosen and the benefits to be realized with the findings of the research. This chapter also lists the main and specific objectives of the research.

Chapter 2 looks into past research related to the current one. The views and findings from other scholars are presented in this chapter, and thereby critiqued, compared and contrasted.

Chapter 3 explores the research methods applied in this current research. The various methods of data collection chosen for the study are also justified

Summary

This chapter presents the background, context, and rationale for the current research. An introduction to the saccharification process of cellulosic waste is given herein, together with the advantages of the process over the normal burning that has for long been used by farmers. The chapter goes ahead to present the research problem and the relevance of the research to the municipal authorities. A list of the main and specific objectives is also given. The next chapter presents a detailed literature review on challenges of waste separation.

Chapter 2

Literature Review

Chapter 1 analyzed the need for this research to be carried by providing some background information on saccharification of cellulosic waste. To be able to critically explore the optimal conditions for the saccharification process, it is worthwhile to look into previous researches by scholars on the topic saccharification. This literature review will divulge the views of other scholars on the concept of solid waste separation using saccharification, contrast the views and critique them as is necessary.

In a study titled Enzymatic Hydrolysis of Waste Cellulose [8], the enzyme Trichoderma viride was produced in submerged fermentation by use of a newspaper as a growth substrate. Various forms of cellulosic material were hydrolyzed by culture filtrates. The rate and degree of hydrolysis was regulated by the degree of crystallinity, particle size, and presence of impurities. Different pretreatment methods were compared, including ball milling, hammer milling and dissolution of cellulose in cuprammonium. It was concluded that due to high costs, low bulk density, the need to keep the substrate wet and the production of other wastes, dissolving cellulose to increase the reaction rate was not a feasible approach.

In another study titled Bioconversion and saccharification of some lignocellulosic wastes by Aspergillus oryzae ITCC-4857.01 for fermentable sugar production [9], three lignocellulolytic substrates - sugarcane bagasse, sawdust and water hyacinth were pretreated with alkali and enzyme and their effect on bioconversion analyzed. The ability of the substrates to induce the cellulase enzyme was also evaluated. Alkali treatment was shown to improve the substrate consumption.

Chapter 3

Research Methods

In the previous chapter, a detailed review of other studies related to saccharification of cellulosic wastes was done. This chapter details the approach used to realize the main and specific objectives of the study. The methods chosen are also justified.

Rice straw will be used as the substrate for this study. This agricultural waste will ideally be crushed, fed into a counter-current extractor, treated with sodium hydroxide and washed with warm water, and finally subjected to enzymatic action. The alkali concentration and temperature conditions will be altered for subsequent trials in a bid to determine the optimal conditions for saccharification.

References

Haque, A., Mujtaba, I. and Bell, J. (2000). A simple model for complex waste recycling scenarios in developing economies. Waste Management, 20(8), pp.625-631.

Andrews, A., Gregoire, M., Rasmussen, H. and Witowich, G. (2013). Comparison of recycling outcomes in three types of recycling collection units. Waste Management, 33(3), pp.530-535.

Alternative to waste incineration. (2002). Filtration & Separation, 39(2), p.22.

Roche, C., & Stickel, J. (2009). High-solids enzymatic saccharification screening method for lignocellulosic biomass. National Renewable Energy Laboratory.

Trzcinski, A. Biofuels from food waste.

Árnadóttir, Á., Kok, G., van Gils, S. and ten Hoor, G. (2018). Waste Separation in Cafeterias: A Study among University Students in the Netherlands. International Journal of Environmental Research and Public Health, 16(1), p.93.

Mandels, M., Hontz, L., & Nystrom, J. (2004). Enzymatic Hydrolysis of Waste Cellulose. U. S. Army Natick Laboratories, XVI, 1471-1493. Retrieved 9 March 2020

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