Bioconversion of Straw into Improved Fodder: Preliminary Treatment of Rice Straw Using Mechanical, Chemical and/or Gamma Irradiation

Abstract

Crude protein (CP) content of mechanically ground rice straw into small particles by an electric grinder and reducing value (RV) and soluble protein (SP) in the culture filtrate were lower than that of the chopped straw into 5~6 cm lengths when both ground and chopped straws were fermented with Aspergillus ochraceus, A. terreus or Trichoderma koningii, at steady conditions. The reduction rate of RV, SP and CP was 22.2, 2.4, 7.3%; 9.1, 4.9, 8.5% or 0.0, 0.0, 3.6% for the three fungi, respectively. Chemical pretreatment of straw by soaking in NH4OH for a day caused significant increase in CP of the fermented straw than the other alkali and acidic pretreatments. Gamma irradiation pretreatment of dry and wet straw with water, specially at higher doses, 100, 200 or 500 kGy, caused significant increase in RV and SP as CP in the fermented straw by any of these fungi. Chemical-physical combination pretreatment of rice straw reduced the applied dose of gamma irradiation required for increasing fermentable ability of fungi from 500 kGy to 10 kGy with approximately the same results. Significant increases in RV and SP of fermented straw generally occurred as the dose of gamma irradiation for pretreated straw, which combined with NH4OH, gradually rose. Whereas, the increase percentage in CP of fermented straw that was pretreated by NH4OH-10 kGy was 12.4%, 15.4% or 8.6% for A. ochraceus, A. terreus or T. koningii, respectively.

Bioethanol Production from Rice Straw Enzymatically Saccharified by Fungal Isolates, Trichoderma viride F94 and Aspergillus terreus F98

“…Thes results have been confirmed by the results of Helal [32]; pretreatment before fungal hydrolysis increases the surface area of the cellulose by reducing particle size.…”

“…According to Helal [32], ionizing radiation as γ lowers the degree of the polymerization of cellulose and lignin and partially disrupts the ligno-cellulosic complex.…”

Characterization of a thermostable β-glucosidase from Aspergillus fumigatus Z5, and its functional expression in Pichia pastoris X33

“…However, without appropriate treatment, a mass of agricultural, industrial and municipal cellulosic wastes has accumulated, resulting in the risk of environmental pollution [ 6 ]. Various methods, such as composting, mechanical treatment and chemical treatment, have been applied to treat these cellulosic wastes [ 7 , 8 ]. Ethanol production from lignocellulosic biomass has received much attention due to the immense potential for conversion of renewable biomaterials into biofuels and chemicals [ 9 ].…”

Prospects for Irradiation in Cellulosic Ethanol Production

“…Similar results were shown by wheat straw when treated using gamma rays along with crushing [ 30 ]. A study by Helaln [ 31 ] indicated increase in the contents of reducing sugar (4-fold) and soluble and crude protein after pretreatment of rice straw with gamma radiations followed by its saccharification with A. ochraceus , A. terreus , or T . koningii .…”