Studies on the Utilization of Single Cell Proteins

Part III. On the enzyatmic digestion of the activated sludge preheated with dilute acid

Abstract

For the utilization of protein in the surplus activated sludge, the conditions to liberate the amino acids from the sludge protein were investigated employing pronase (proteinase from Str. griceus) to digest for 72 hours at 50°C after mild hydrolysis with dilute hydrochloric acid or sulfuric acid.
For the liquefaction over 80% of total nitrogen of the sludge, the following conditions of preheating with acids are necessary: 1) 10ml/g of acid over 0.5N for 60 minutes or 1N for 30 minutes at 120°C and 0.25N for 60 minutes or 0.5N for 30 minutes at 140°C. 2) 60ml/g of acid over 0.1N for 60 minutes or 0.5N for 30 minutes at 120°C and 0.01N for 60 minutes or 0.05N for 30 minutes at 140°C. The residual rates of tryptophan in the sludge on the pretreatment at 140°C for 60 minutes under 1N of acids in the above conditions were over 30% of the total amount in the sludge. (Received Dec. 9, 1971)