Growth of Rhizopus delemar UICC 27, UICC 67, and UICC 121 on the slurry and palm kernel cake mixtures

There have reports of treatment of crude palm oil (palm oil) and by-products in the form of waste as substrates for Rhizopus. This study investigated the ability of three strains of Rhizopus delemar (UICC 27, UICC 67 and UICC 121) to grow on and ferment wastes from palm oil processing. The wastes were consisted of sterile mixtures of slurry and palm kernel cake (3:1). The initial cell number for fermentation was 1×107 CFU/mL, with 10% (v/w) inoculum concentration and 20 g final weight of mixtures. The fermentation was carried out for five days at 28 °C. All three strains of Rhizopus delemar were able to grow on and ferment the sterile mixtures of slurry and kernel cake (3:1). Rhizopus delemar UICC 67 showed the fastest growth and reached the highest number of cells of 6.09×108 CFU/mL, followed by the growth and increased number of cells of R. delemar UICC 27 and UICC 121 of 3.60×108 CFU/mL. This study showed that R. delemar strains have the ability to grow and ferment agro-industrial waste such as palm oil processing waste. Further study is required to determine the effect of fermentation by R. delemar on the nutrient content of palm oil waste.