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Biotransformation via solid state fermentation (SSF) mediated by microorganisms is a promising approach to produce useful products from agricultural biomass. Lactic acid bacteria (LAB) that are commonly found in fermented foods have been shown to exhibit extracellular proteolytic, &#946;-glucosidase, &#946;-mannosidase, and &#946;-mannanase activities. Therefore, extracellular proteolytic, cellulolytic, and hemicellulolytic enzyme activities of seven <i>Lactobacillus plantarum</i> strains (a prominent species of LAB) isolated from Malaysian foods were compared in this study. The biotransformation of palm kernel cake (PKC) biomass mediated by selected <i>L. plantarum</i> strains was subsequently conducted. The results obtained in this study exhibited the studied <i>L. plantarum</i> strains produced versatile multi extracellular hydrolytic enzyme activities that were active from acidic to alkaline pH conditions. The highest total score of extracellular hydrolytic enzyme activities were recorded by <i>L. plantarum</i> RI11, <i>L. plantarum</i> RG11, and <i>L. plantarum</i> RG14. Therefore, they were selected for the subsequent biotransformation of PKC biomass via SSF. The hydrolytic enzyme activities of treated PKC extract were compared for each sampling interval. The scanning electron microscopy analyses revealed the formation of extracellular matrices around <i>L. plantarum</i> strains attached to the surface of PKC biomass during SSF, inferring that the investigated <i>L. plantarum</i> strains have the capability to grow on PKC biomass and perform synergistic secretions of various extracellular proteolytic, cellulolytic, and hemicellulolytic enzymes that were essential for the effective biodegradation of PKC. The substantial growth of selected <i>L. plamtraum</i> strains on PKC during SSF revealed the promising application of selected <i>L. plantarum</i> strains as a biotransformation agent for cellulosic biomass.