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ACTINOMYCETES AS A SOURCE OF NOVEL ENZYMES FOR LIGNOCELLULOSE BIOCONVERSION

Objective

CREATION OF STRAIN AND DATA BANKS AS A SOURCE OF MATERIAL AND INFORMATION ON THE POTENTIAL OF ACTINOMYCETES IN LIGNOCELLULOSE DEGRADATION PROCESSES.
DEMONSTRATION OF IMPROVED SACCHARIFICATIONS RATES USING SELECTED COMBINATIONS OF ENZYMES FROM DIVERSE SOURCES. IDENTIFICATION OF ENZYMES WHICH DESIRABLE PROPERTIES FOR PROCESS DEVELOPMENT. E.G. THERMOSTABILITY. A FIRM BASIS FOR STRAIN IMPROVEMENT AND SCALE-UP STUDIES ON EFFICIENT ACTINOMYCETE SACCHARIFICATION SYSTEMS.
This research programme has been directed towards the analysis of actinomycete enzyme systems involved in the degradation of plant biomass (lignocellulose). The programme was innovative in 2 respects: a novel source of enzymes (ie actinomycetes) was systematically screened; wheat straw saccharifying activity, rather than the production of particular enzymes, was the criterion used.
Over 200 actinomycete strains representing a broad taxonomic range were screened. Common features included optimal saccharifying activity in the pH range 6-9 and the identification of xylose oligomers as the principal products. Increased stability at 70 C was a feature of enzyme preparations from thermophilic strains. A range of specific enzyme activities were involved and included cellulase, xylanase, arabinofuranosidase, acetylesterase, ss-xylosidase and ss-glucosidase. With the exception of the latter 2 enzymes, saccharification was mainly located in culture supernatants. Since hemicellulose (arabinoxylan) was clearly the primary source of sugar, the xylanases produced by a range of strains were characterised. In all cases, enzyme activity was inducible and xylan hydrolysis resulted mainly from endoxylanase activity which was susceptible to end product inhibition. The xylan degrading systems of actinomycetes were complex and nonuniform, with up to 6 separate endoxylanases identified in active strains.

This research programme has been directed towards the analysis of actinomycete enzyme systems involved in the degradation of plant biomass (lignocellulose). The programme was innovative in 2 respects: a novel source of enzymes (ie actinomycetes) was systematically screened; wheat straw saccharifying activity, rather than the production of particular enzymes, was the criterion used.
Over 200 actinomycete strains representing a broad taxonomic range were screened. Common features included optimal saccharifying activity in the pH range 6-9 and the identification of xylose oligomers as the principal products. Increased stability at 70 C was a feature of enzyme preparations from thermophilic strains. A range of specific enzyme activities were involved and included cellulase, xylanase, arabinofuranosidase, acetylesterase, ss-xylosidase and ss-glucosidase. With the exception of the latter 2 enzymes, saccharification was mainly located in culture supernatants. Since hemicellulose (arabinoxylan) was clearly the primary source of sugar, the xylanases produced by a range of strains were characterised. In all cases, enzyme activity was inducible and xylan hydrolysis resulted mainly from endoxylanase activity which was susceptible to end product inhibition. The xylan degrading systems of actinomycetes were complex and nonuniform, with up to 6 separate endoxylanases identified in active strains.
DR ANDREW BALL WAS APPOINTED AS A RESEARCH ASSISTANT FOR THE DURATION OF THIS CONTRACT ON 1ST OCTOBER 1986. WITH THE PART-TIME ASSISTANCE OF A TECHNICIAN PROVIDED BY THE UNIVERSITY OF LIVERPOOL AND UNDER THE SUPERVISION OF DR MCCARTHY, THE RESEARCH IS PROCEEDING AS PLANNED.
WE HAVE OBTAINED AND PREPARED SAMPLES OF MILLED CEREAL STRAW AND ARE CURRENTLY EVALUATING OUR "IN HOUSE" STRAIN BANK FOR SACCHARIFYING ACTIVITY. THE COMPARATIVE ABILITY OF A RANGE OF MESOPHILIC AND THERMOPHILIC ACTINOMYCETE STRAINS TO GENERATE SUGARS FROM STRAW IS BEING DETERMINED AS A PREREQUISITE TO STRAIN SELECTION. WE HAVE IDENTIFIED STRAINS WHOSE LEVEL OR TYPE OF ACTIVITY AGAINST STRAW WARRANTS MORE DETAILED CHARACTERISATION. STRAINS SELECTED ON THIS PRELIMINARY BASIS HAVE BEEN DESPATCHED TO OUR COLLABORATORS (DR M J PENNINCKX, UNIVERSITY OF BRUSSELS - CONTRACT NO EN3B007900) FOR PHYSIOLOGICAL CHARACTERISATION AND WE HAVE ALSO ADDED STRAINS FROM BRUSSELS TO OUR STRAIN BANK.
REPRTHE FINAL PART OF THIS PRELIMINARY SELECTION PROCESS WILL INVOLVE THE ISOLATION OF NEW STRAW-DEGRADING ACTINOMYCETES FROM COMPOST SAMPLES WHICH WE HAVE NOW RECEIVED FROM OUR COLLABORATORS IN BRUSSELS.

THE LATER PHASES OF THE PROJECT WILL CONCENTRATE ON THE CHARACTERISATION OF EXTRACELLULAR PROTEINS WITH ENZYME ACTIVITY AND WE ARE CURRENTLY EVALUATING PROTEIN SEPARATION SYSTEMS, USING THERMOSTABLE ACTINOMYCETE XYLANASES AS MODELS. WE HAVE PURCHASED A FAST PROTEIN LIQUID CHROMATOGRAPHY SYSTEM FOR PROTEIN SEPARATION AND THIS WILL BE INSTALLED IN JANUARY 1987. WE HAVE IN CONSTANT CONTACT WITH DR PENNINCKX'S GROUP AND DR J COOMBS REPRESENTING THE EEC AND MET AS A GROUP IN DECEMBER 1986 AT LIVERPOOL. ALL PROCEDURES HAVE BEEN STANDARDISED AND BOTH GROUPS WILL NOW USE BELGIAN WHEAT STRAW, CHOPPED OR BALL-MILLED AT LIVERPOOL.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

THE UNIVERSITY OF LIVERPOOL
Address
Senate House, Abercromby Square
L69 3SG Liverpool
United Kingdom

Participants (1)

UNIVERSITE LIBRE DE BRUXELLES (ULB)
Belgium