The linamarase of Mucor circinelloides LU M40 and its detoxifying activity on cassava

Authors


Prof. F. Federici, Dipartimento di Agrobiologia e Agrochimica, University of Tuscia, Via S.C. De Lellis, 01100 Viterbo, Italy (e-mail: federici@unitus.it).

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.

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