BIOCONVERSION OF HEMICELLULOSES OF RICE HULL BLACK LIQUOR INTO SINGLE-CELL PROTEIN

Rice hulls were treated using several sodium hydroxide concentrations and temperatures. The black liquor contents of silica, lignin and hemicelluloses increased with increase in temperature or sodium hydroxide concentration. Hexoses constituted the major part and pentoses the minor part of the black liquor hemicelluloses. The ratio of pentoses to hexoses increased slightly with the increase of treatment variables. The pentose content of the black liquor consisted of arabinose and xylose, while the hexose composition was mannose, galactose, rhamnose and glucose. On increasing the alkali concentration, the xylose and mannose concentrations increased greatly, while galactose and glucose increased only slightly. Using 10 soil samples several isolates of fungi and actinomycetes were obtained. These were identified as five species of the genus Aspergillus, three species of Paecilomyces, two species of Penicillium, one species each of Alternaria, Trichoderma, Chaetomium and Actinopolyspora. These fungi were cultivated on black liquor basal salts medium. The highest bioconversion rate of black liquor hemicelluloses into biomass and single-cell proteins was achieved by Aspergillus terreus, followed by Paecilomyces simplicissima then Actinopolyspora sp.