Date of Award

1980

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Experiments have been conducted to determine the feasibility of the bioconversion of cellulose into Single Cell Protein (SCP) using a thermotolerant, cellulolytic strain of Aspergillus terreus. Crude cellulases produced during the growth of fungal biomass were tested for their ability to generate glucose syrups by enzymatic hydrolysis of cellulose. Studies on continuous cultivation of glucose-limited A. terreus resulted in the development of a highly optimized medium which allowed the organism to achieve similar maximum specific growth rates (umax) measured in batch culture. Upon proportionate increase of the medium composition, there was no decrease in growth rates or in biomass yields from glucose (Y(,glucose)). Macromolecular analysis of glucose-limited A. terreus demonstrated that protein and RNA content increased while cell carbohydrate decreased with increasing growth rates. DNA content decreased with increasing growth rates but sharply increased at high growth rates. Batch, semi-continuous, and continuous cultivation of cellulose-grown A. terreus showed that 78-88% of the available cellulose was utilized with the biomass containing 32-35% crude protein. In batch and semi-continuous cultivation studies, the minimum doubling time was measured at 7.3 hours while under continuous cultivation conditions, the biomass doubling time was 5 hours. Maximum saccharification of cellulose by crude cellulases of A. terreus was obtained at a temperature of 50C and pH 4. Under these conditions, 70-75% of the available cellulose was converted into syrups containing 7.0-7.5 g/l glucose. Addition of varying concentrations of different trace metals showed no further stimulation of cellulase activity suggesting that adequate concentrations were already present. Scale-up of saccharification experiments resulted in the production of syrups containing 40 g/l glucose. These data suggest that the SCP and saccharification processes are competitive with and in some aspects, superior to existing processes.

Pages

87

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