Study Of Ethanol Production From Fungal Pretreated Wheat And Rice Straw

摘要

Bioconversion offers a cheap and safe method of not only disposing the agricultural residues, but also it has the potential to convert lignocellulosic wastes into usable forms such as reducing sugars that could be used for ethanol production. This paper reports a preliminary study on the microbial pretreatment and fermentation of the agricultural residues like wheat straw, rice straw. A combination of five different fungi viz. Aspergillus niger , Aspergillus awamori , Trichoderma reesei, , Phenerochaete chrysosporium, Pleurotus sajor-caju, obtained from screening were used for pretreatment and Saccharomyces cereviseae (NCIM 3095) was used for carrying out fermentation. In case of Wheat straw and rice straw, pretreatment with Aspergillus niger and Aspergillus awamori and later fermentation yielded highest amount of ethanol(2.5gl-1 & 2.2g l-1 respectively ). Introduction Bioethanol produced from renewable biomass has received considerable attention in current years. Using ethanol as a gasoline fuel additive as well as transportation fuel helps to alleviate global warming and environmental pollution. In the last decade, most research has tended to focus on developing an economical and ecofriendly ethanol production process. Much emphasis is being given to the production of ethanol from agricultural and forestry residues and other forms of lignocellulosic biomass.(Kadam et al. 2000). Changes in how agricultural field residues are managed further complicate farming economies. In the past, disposal of straw by burning was an accepted practice. This practice is now being challenged due to concern over the health effects of smoke from burning fields. Further the cellulosic plant material represents an as–of–yet untapped source of fermentable sugars for significant use, especially non-food lignocellulosic waste products like wheat straw, rice straw, baggasse, rice husk etc. In these waste products, the polysaccharides, cellulose and hemicellulose are intimately associated with lignin in the plant cell wall(Ballerini.et al. 1994). The lignin component acts as a physical barrier and must be removed to make the carbohydrates available for further transformation processes. Therefore, the pretreatment is a necessary process for utilization of lignocellulosic materials to obtain ultimately high degree of fermentable sugars.Bioconversion of cellulosic biomass into fermentable sugar, for production of ethanol using microorganisms, especially cellulose degrading fungi, makes bioethanol production economic, environmental friendly and also renewable.Cellulose is the major constituent of organic matter of plant origin. Lignocellulosic materials are most abundant and renewable resources on earth, which makes them attractive for production of ethanol (Zsolt Szengyel 2000).Pretreatment is an important tool for practical cellulose conversion processes. Pretreatment is required to alter the structures of cellulosic biomass to make more accessible to the enzymes that convert the carbohydrate polymers into fermentable sugars (Mosier et al. 2005) and to cellulase producing microorganisms. There are several ways to increase the digestibility of cellulose before it is exposed to enzyme or microbial conversion: mechanical, physical chemical or biological pretreatment, as well as the combination of these methods (Bollok 1999).In this work a study is made on the ethanol production from raw materials which have been treated with various combination of the fungal strains obtained after screening. Materials And Methods Raw materials Wheat straw obtained from local fields of Davanagere districtRice straw from local fieldsEach raw material was powdered and sieved into a 1mm seiver. Powder of each raw material was used as carbon source. Microorganisms : Screening of cellulose degrading fungi was done from the soil samples of local paddy and wheat fields and five of such fungi were selected viz. Aspergillus niger, Aspergillus awamori, Trichoderma reesei, Phenerochaet