Cellulase fermentation on a novel substrate (waste cardboard) and subsequent utilization of home-produced cellulase and commercial amylase in a rabbit feeding trial

Abstract

Cellulase and amylase enzymes are increasingly being used as feed additives in animal nutrition. Those are mainly applied in order to improve the nutritional value of feed by partially degrading its fiber content, which has major importance during the early post-weaning period of young animals possessing inadequate digestive enzyme activities. Due to their commercial availability at low cost, the utilization of amylases as animal feed additive can be highly recommended, while the high price of cellulases actually makes their use as a feed additive unreasonable. A promising way to gain cheap cellulases is to conduct the enzyme fermentation process on novel substrates, which are readily available at no cost. In this study, the utilization of old corrugated cardboard (OCC) as a novel fermentation substrate has been investigated for cellulase enzyme fermentation by Trichoderma reesei Rut C-30. Batch fermentation experiments were carried out in shake-flasks and in a 30 l laboratory fermenter. The OCC feedstock proved to be a suitable fermentation substrate, a filter paper activity (FPA) of as high as 2.27 FPU ml −1 was achieved in the fermenter, which corresponds to a yield of 227 FPU g −1 cellulose. The maximum productivity achieved was 35.7 FPU l −1 h −1. The subsequent utilization of this cellulase enzyme preparation was investigated as additive of commercial rabbit compound feed in order to improve its digestibility during the early post-weaning period. In parallel, commercial amylase preparations were also tested for the same purposes. The results of animal feeding experiments showed, that enzyme supplementation of the complete feed improved production traits, as it increased the digestibility of nutrients and thus reduced the mortality caused by digestive disorders.