Khek Han Wen, Goh Zi Yi, Noraziah Abu Yazid, Rohana Abu and Siti Hatijah Mortan

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EFFECT OF BULKING AGENT AND INOCULUM SIZE ON NUTRIENT CONTENT OF FERMENTED PALM KERNEL CAKE  

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Abstract 

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Palm kernel cake (PKC) contains protein, fats, minerals, and carbohydrates which makes it a suitable feed ingredient for poultry and ruminants. However, PKC contains approximately 15‒25% crude fibre, which limits its efficiency as animal feed. Fermenting PKC for animal feed is essential to boost their nutrient value and decrease fibre, which helps improve digestion and support animal growth.  This study was done to identify the effect of inoculum size and bulking agent on the nutrient contents of fermented PKC through solid-state fermentation (SSF) using Rhizopus oligosporus. The experiment was carried out using different bulking agents (plastic straw, rice straw, sugar cane bagasse, coconut wood chip) and inoculum sizes (1.5 wt% to 7.5 wt%). The soluble protein content was quantified using Bradford assay. The results showed that sugar cane bagasse, as a bulking agent, had the highest soluble protein (3.36 mg/g), reducing sugar (7.46 mg/g), and total phenolic content (TPC) (13.01 mg/g), with a reduction in crude fiber from 19.57% to 15.88%. The best inoculum size was found at 4.5 wt%, with the highest soluble protein (2.86 mg/g), the second-highest reducing sugar (9.42 mg/g), TPC (15.16 mg/g), and crude fiber reduction to 12.50%. Lactic acid shows minimal differences across bulking agents and inoculum sizes, with values within ±0.2 mg/g. In conclusion, it was found that the best bulking agent for PKC fermentation is sugar cane with the best inoculum size of Rhizopus oligosporus at 4.5 wt%. (235 words).

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