Abstract

Background and Aim: Palm kernel meal (PKM), a major by-product of the palm oil industry, is rich in nutrients but poorly utilized in poultry feed due to its high fiber and mannan content. Improving PKM digestibility through microbial bioconversion could reduce dependency on expensive protein sources, such as soybean meal. This study aimed to evaluate a consortium of Bacillus subtilis and Lactobacillus fermentum for its enzymatic activity, probiotic properties, and potential to enhance PKM utilization in poultry diets.

Materials and Methods: The research was performed in four stages: (1) measurement of cellulase, mannanase, and protease activities in individual and combined bacterial cultures (seven treatments, five replications); (2) determination of enzyme activities in B. subtilis and L. fermentum (1:1) grown in de Man, Rogosa, and Sharpe broth supplemented with 0%–20% PKM (four treatments, seven replications); (3) in vitro probiotic characterization, including acid and bile tolerance, hydrophobicity, autoaggregation, coaggregation, and pathogen inhibition; and (4) evaluation of enzyme activity in natural media composed of coconut water and shrimp wastewater. Data were analyzed using analysis of variance and Duncan’s multiple range tests at p < 0.05.

Results: The 1:1 consortium exhibited the highest enzyme activities; cellulase (13.71 U/mL), mannanase (17.05 U/mL), and protease (9.32 U/mL). The consortium retained high activity in 15% PKM media and demonstrated strong acid tolerance (70.6% survival at pH 2.5), bile salt tolerance (62.84% at 0.3%), and thermal resistance (83.15% at 42°C). It showed 83.75% hydrophobicity, 73.32%–71.64% autoaggregation, and 78.13% coaggregation, along with marked inhibition against Escherichia coli, Salmonella Enteritidis, and Staphylococcus aureus (15.07–17.12 mm inhibition zones). Natural media composed of 70% coconut water + 30% shrimp wastewater supported optimal enzymatic performance.

Conclusion: The B. subtilis–L. fermentum consortium demonstrates potent synergistic enzymatic and probiotic traits, indicating its suitability as a bioenhancer for PKM-based poultry feed. This dual-function probiotic could lower feed costs, improve nutrient digestibility, and support sustainable poultry production. Future work should validate these results through in vivo trials and large-scale fermentation optimization.

Keywords: Bacillus subtilis, consortium, enzyme activity, Lactobacillus fermentum, palm kernel meal, poultry feed, probiotic.