PROJECT REPORT
PROCESS DEVELOPMENT FOR PRODUCTION AND
STABILIZATION OF FEED ENZYMES
National Diploma in Biotechnology
Supervisor
: Mr. D.M. Ramduth (CSIR)
Co-supervisor
: Dr. L. Reddy (DUT)
by
Sabelo L. Khuzwayo
CSIR Bioscience, Private Bag x2, Modderfontein, 1645
Tel : +27 11 605 2696
Fax : +27 11 608 3020
ABSTRACT
Xylanase and cellulase are hydrolytic enzymes that are widely used in many industrial
processes to breakdown plant polysaccharides such as xylan and cellulose. These
enzymes have been found to result in enhanced digestion when added to animal feeds.
However, large-scale use of these enzymes is hindered by production costs and poor
stability of the enzyme product during storage. Aspergillus carneus (Abo 374)
producing a cocktail of these enzymes was isolated by the University of Stellenbosch.
This isolate was capable of utilizing corn steep liquor (CSL) as a nitrogen source and
wheat straw as a carbon source in submerged fermentation. In this study, three CSL
types [Spray-dried (CSLSD), Phytase-treated (CSLPT), and Phytase-treated and ultrafiltered (CSLPTUF)] were evaluated for their effect on the production levels of
xylanase and cellulase. The results showed that the difference between the three
treatments was statistically significant (P<0.05). CSLPT resulted in high xylanase
levels (5458 nKat.ml-1) compared to CSLSD (4990 nKat.ml-1) and CSLPTUF (3908
nKat.ml-1). However, when tested at lab-scale, xylanase activity dropped by 63%
whereas cellulase activity increased by 51%. Further investigation was carried out to
develop an economical stabilization technique. In this study, freeze-drying and
agglomeration were evaluated to determine their capacity to stabilize enzymes at low
costs. Maximum xylanase recovery of 84% and cellulase recovery of 102% was
obtained when Carrier A was used in agglomeration process. Freeze-drying resulted
in xylanase and cellulase recoveries of 121% and 117% respectively. Although both
techniques were found to be highly effective, agglomeration was identified as a more
favorable method as freeze-drying was time consuming and uneconomical.
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