S Patel, R Onkarappa, S Gurumurthy
dns, fungi, pretreatment, reducing sugars
S Patel, R Onkarappa, S Gurumurthy. Pretreatment studies on wheat straw and rice straw. The Internet Journal of Microbiology. 2008 Volume 7 Number 1.
Pretreatment is a necessary process for utilization of lignocellulosic materials to obtain ultimately high degree of fermentable sugars. In this work comparative study of chemical and microbiological treatments on the wheat and rice straw is carried out. Alkaline and acid treatments were selected as chemical treatments. Six fungi
Cellulose is the most abundant carbohydrate polymer in wastes from forest products agriculture, fruits, and vegetables. Agricultural wastes and in fact all lignocellulosics can be converted into products that are of commercial interest such as ethanol, glucose, single cell protein (Solomon
Materials and Methods
Substrates: Wheat straw and rice straw were obtained from local fields of Davanagere district. Each raw material was powdered and sieved into a 1mm sieve and this was used as carbon source.
Isolation of fungi: Screening of fungi capable of degrading cellulose was done (Abdul
Acid hydrolysis and saccharification
One hundred gram of dried sample was weighed into 2000 ml conical flasks and 1000 ml of sulphuric acid were added to the conical flask. The flasks were covered with aluminium foil and heated for two hours on flame. The flask was allowed to cool and filtered through Whatman No.1 filter paper. The pH was adjusted to 4.5 with 0.4 M sodium hydroxide (Humphrey and Caritas 2007).
One hundred gram of dried sample was weighed into 2000 ml conical flask and 1000 ml of 0.25 M sodium hydroxide solution was added to the conical flask .The flask was left for one hour, after which the mixture was neutralized with 0.1 M hydrochloric acid (HCL) to a pH of 4.5. The flask was allowed to cool at room temperature and filtered through Whatman No.1 filter paper.
Mandles medium was prepared by adding (gl-1): urea 0.3, (NH4)2SO4 1.4, KH2PO4 2, CaCl2 0.3, MgSO47H2O 0.3, bacto peptone 0.75, and yeast extract 0.25. Trace elements were also added, using a 1% (v/v) solution of salts(mll-1):FeSO47H2O 0.5, MnSO4 0.16, ZnSO4 0.14, CoCl2 2. pH was adjusted to 5.5-6.0 before sterilization (Bollok and Reczey 2000).
10g /l of each residue was taken in conical flask containing 200ml of Mandle’s medium. The conical flasks were plugged with cotton and sterilized at 15lbs per sq.inch for 20 minutes. Each flask was inoculated with 4-5 discs of different fungi. These flasks were incubated at room temperature for 5days on an orbital shaker. After five days mycelium was separated by filtration through Whatman filter paper No.1. The filtrate was used for further studies (Harpreet
Determination of total carbohydrate: The carbohydrate content of untreated and pretreated raw materials in the culture broth was measured by phenol sulphuric acid method (Thimmaiah, 1999) with glucose as standard.
Determination of reducing sugars: Reducing sugars in untreated and pretreated raw materials in the culture broth were determined by dinitrosalicylic acid (DNS) method (Miller, 1959) with glucose as standard.
Results and discussion
Initial composition of the raw materials was determined (Table 1). Pretreatment of raw materials makes it accessible for microbial treatment. So chemical treatments were conducted (table 2). Results of fungal treatments are shown in table 3.
Autoclaving for sterilization has affected and resulted in increase in sugar release. With fungal treatment still increase in the yield of sugars was observed. Treatments with