The aim of this study was to evaluate whether pretreatment of palm kernel meal (PKM) with a commercial feed enzyme (Allzyme Vegpro ) or solid-state fermentation of PKM with the cellulolytic fungus Trichoderma koningii (Oudemans) could improve the nutritive value of raw PKM in the diets of red hybrid tilapia, Oreochromis sp. Seven isonitrogenous (30% crude protein) and isoenergetic (15.1 kJ g À1 ) practical diets were formulated and fed close to apparent satiation to triplicate groups of 14 fish (mean initial weight 5.1 + 0.1 g) for 10 weeks. The diets consisted of a control diet which did not contain any PKM, raw PKM diets, enzyme-treated PKM (EPKM) or fermented PKM (FPKM) diets at 20% and 40% (dry weight basis) inclusion rates. The growth performance and feed utilization efficiency of tilapia fed 20% PKM or 20% EPKM were not significantly different (P > 0.05) from those of fish fed the control diet. Fish fed diets containing 40% EPKM showed significantly higher growth and feed utilization efficiency than fish fed 40% raw PKM owing to the improved dry matter, protein, lipid and energy digestibility of the enzymetreated PKM diets. The apparent protein and lipid digestibility of the 20% EPKM and 40% EPKM diets were not significantly different, and nor was the growth and feed utilization efficiency of fish fed these two diets. Hybrid tilapia fed FPKM-based diets at all dietary inclusions tested showed the poorest growth, and this might indicate the presence of antinutrients in the resultant fungal biomass. In conclusion, it is anticipated that, with further optimization of enzyme pretreatment of PKM, higher levels of PKM could be included in the diets of hybrid tilapia, thereby reducing the impact of rising costs to feed tilapia.

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An assessment of the nutritive value of palm kernel meal (PKM) and aflatoxin‐contaminated PKM (obtained by fermenting PKM with Aspergillus flavus) as a dietary ingredient in pelleted feed for tilapia, Oreochromis mossambicus Peters, was carried out in a 12‐week feeding trial. Seven isonitrogenous (40% crude protein) and isoenergetic (15.1 kJ g−1) practical diets were formulated and fed close to apparent satiation to triplicate groups of 12 fish (mean initial weight 8.4 ± 0.1 g). The control diet contained 30% fish meal and 10% soybean meal (SBM) proteins. Four other experimental diets containing 20% and 50% of the SBM protein replaced by either PKM or fermented PKM, respectively, were formulated. Two additional diets containing either PKM or fermented PKM supplemented with a commercial aflatoxin adsorber (0.5% SorbatoxTM) were also formulated. Measured aflatoxin B1 levels in the fermented PKM‐based diets ranged from 75 to 100 µg kg−1 diet. The growth performance and feed utilization efficiency of tilapia fed fermented PKM‐based diets were significantly lower than in fish fed the control diet at all inclusion levels (P < 0.05). Despite a small reduction, weight gains of tilapia fed PKM‐based diets were not significantly different compared with fish fed the control diet. The addition of 0.5% Sorbatox did not produce any beneficial or negative effects to the growth of tilapia. Under the dietary conditions of the present experiment, it was concluded that PKM can substitute up to 50% SBM in practical diets for O. mossambicus without much adverse effect to fish growth. However, when PKM was contaminated with A. flavus, its' incorporation into tilapia diets resulted in growth depression as a result of decreased diet digestibility and also possibly because of the presence of anti‐nutrients found in the contaminated PKM.

Novel design solid state bioreactor, FERMSOSTAT, had been evaluated in cellulase production studies using local isolate Aspergillus niger USM AI 1 grown on sugarcane bagasse and palm kernel cake at 1 : 1 (w/w) ratio. Under optimised SSF conditions of 0.5 kg substrate; 70% (w/w) moisture content; 30°C; aeration at 4 L/h · g fermented substrate for 5 min and mixing at 0.5 rpm for 5 min, about 3.4 U/g of Filter paper activity (FPase) was obtained. At the same time, comparative studies of the enzymes production under the same SSF conditions indicated that FPase produced by A. niger USM AI 1 was about 35.3% higher compared to Trichoderma reesei. This shows that the performance of this newly designed SSF bioreactor is acceptable and potentially used as prototype for larger-scale bioreactor design.

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