The linamarase of<i>Mucor circinelloides</i>LU M40 and its detoxifying activity on cassava

Abstract

Mucor circinelloides LU M40 produced 12·2 mU ml−1 of linamarase activity when grown in a 3 l fermenter in the following optimized medium (g l−1 deionized water): pectin, 10·0; (NH4)2SO4, 1·0; KH2PO4, 2·0; Na2HPO4, 0·7; MgSO4.7H2O, 0·5; yeast extract, 1·0; Tween‐80, 1·0, added after 48 h of fermentation. The purified linamarase was a dimeric protein with a molecular mass of 210 kDa; the enzyme showed optimum catalytic activity at pH 5·5 and 40 °C and had a wide range (3·0–7·0) of pH stability. The enzyme substrate specificity on plant cyanogenic glycosides was wide; the Km value for linamarin was 2·93 mmol l−1. The addition, before processing, of the fungal crude enzyme to cassava roots facilitated and shortened detoxification; after 24 h of fermentation, all cyanogenic glycosides were hydrolysed.