Large Scale Production of Acid Proteinases by Humicola Lutea 120–5

ABSTRACT

The fungal mutant strain Humicola lutea 120–5 was able to produce high level of acid proteinases in shake flask cultures using as carbon source more inexpensive substrates than glucose. Of the substrates tested (corn starch, glucose-fructose syrups and maltodextrines) corn starch in concentration 3 % was found to be the best carbon source ensuring 60 % drop in the price of medium compared with the basal fermentation medium (containing 4 % glucose) and 100 % preservation of the level of proteolytic activity (1000 PU/ml) in the culture broth. Casein only was used as sole nitrogen source (technical product) in concentration 0,4 % instead of 0,3 % casein + 0,4% soybean meal. The laboratory results have been successfully scaled up using 15m³ fermentor for industrial production of acid proteinases under trade mark “Humicolin”®. The crude enzyme solution with high activity 28 000 PU/ml concentrate exhibited very satisfactory storage stability after addition of 10% NaCl. The enzyme complex lost only 30 % activity after 6 months at 20 °C. The crude enzyme solution was applied with success in leather industry, as well as for isolation and purification of the two acid proteinases A and B, used in food industry for protein hydrolysis.