Review
Cellulases: Biosynthesis and applications

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Abstract

Strains of Trichoderma, particularly T. reesei and its mutants, are good sources of extracellular cellulase suitable for practical saccharification. They secrete a complete cellulase complex containing endo- and exo-glucanases plus β-glucosidase (cellobiase) which act syngergistically to degrade totally even highly resistant crystalline cellulose to soluble sugars. All strains investigated to date are inducible by cellulose, lactose, or sophorose, and all are repressible by glucose. Induction, synthesis and secretion of the β-glucanase enzymes appear to be closely associated. The composition and properties of the enzyme complex are similar regardless of the strain or inducing substrate although quantities of the enzyme secreted by the mutants are higher. Enzyme yields are proportional to initial cellulose concentration. Up to 15 filter paper cellulase units (20 mg of cellulase protein) per ml and productivities up to 80 cellulase units (130 mg cellulase protein) per litre per hour have been attained on 6% cellulose. The economics of glucose production are not yet competitive due to the low specific activity of cellulase (0.6 filter paper cellulase units/mg protein) and poor efficiency (about 15% of predicted sugar levels in 24 h hydrolyses of 10–25% substrate). As hydrolysis proceeds, the enzyme reaction slows due to increasing resistance of the residue, product inhibition, and enzyme inactivation. These problems are being attacked by use of pretreatments to increase the quantity of amorphous cellulose, addition of β-glucosidase to reduce cellobiose inhibition, and studies of means to overcome instability and increase efficiency of the cellulases. Indications are that carbon compounds derived from enzymatic hydrolysis of cellulose will be used as fermentation and chemical feedstocks as soon as the process economics are favourable for such application.

References (212)

  • A.L. Demain

    J. Appl. Chem. Biotechnol.

    (1972)
  • H. Holzer

    Trends Biochem. Sci.

    (1976)
  • J.S. Huang et al.

    Anal. Biochem.

    (1976)
  • Y.W. Han et al.
  • W.G. Allen
  • M. Mandels et al.

    Process Biochem.

    (1978)
  • J.M. Nystrom et al.
  • L. Spano et al.
  • C.R. Wilke et al.
  • C.R. Wilke et al.
  • C.R. Wilke et al.

    Biotechnol. Bioeng.

    (1976)
  • C.R. Wilke et al.
  • D.E. Brown et al.

    Biotechnol. Bioeng.

    (1975)
  • B. Amsallem

    Int. Biodeterior. Bull.

    (1970)
  • R.E. Andreotti et al.
  • L.E.R. Berghem et al.

    Eur. J. Biochem.

    (1976)
  • J.A. Bernat et al.

    Przem. Ferment. Rolny

    (1977)
  • F. Bissett et al.

    Appl. Env. Microbiol.

    (1978)
  • D.E. Brown

    Octagon Paper

    (1976)
  • D.E. Brown et al.

    Biotechnol. Bioeng.

    (1977)
  • E.E. Bruchmann et al.

    Chem. Ztg.

    (1975)
  • A. Ferrer et al.
  • B.J. Gallo et al.
  • D.S. Gong et al.

    Biotechnol. Bioeng.

    (1977)
  • R.F. Goldberger et al.

    Adv. Genet.

    (1976)
  • T.L. Highley

    Mater. Org.

    (1976)
  • J. Janicki et al.

    Pr. Kom. Nauk. Roln. Kom. Nauk. Lesn., Poznan. Tow. Przyj. Nauk.

    (1976)
  • N.J. King et al.

    Int. Biodeterior. Bull.

    (1973)
  • Komura, I., Awao, T. and Yamada, K. Jan Kokai 77 134 090...
  • Komura, I. and Yamada, K. Jan, Kokai 78 38 689...
  • A. Korculanin et al.

    Mikrobiologija

    (1975)
  • A. Korculanin et al.

    Acta Bot. Croat.

    (1977)
  • M. Lai

    Shih Pin Kung Yeh

    (1977)
  • B.H. Lee et al.

    Appl. Microbiol.

    (1975)
  • M. Leisola et al.

    Biotechnol. Bioeng.

    (1978)
  • M. Linko et al.
  • A.G. Lobanok et al.

    Latv. PSR Zinat. Akad. Vestis

    (1977)
  • Loginova, L. G., Guzhova, E. P., Ismailova, D. Yu and Burdenko, L. G. 1978, 14,...
  • M. Mandels
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