Lipolytic Activities of Bacteria Isolated from Oil Palm Fruit Heaps Obtained in Towns of Five Local Government Areas of Rivers State, Nigeria

Abstract

Oil palm fruit heap wastes contain various microorganisms with high lipolytic potential and opportunities for biotechnological uses. Although there has been a growing interest in bacterial lipase, very little is known about the types and lipolytic capacities of the bacteria that are associated with oil palm fruit heaps. This research evaluated the lipase activity of bacterial isolates in heaps of oil palm waste in different locations in Rivers State, such as Owerewere, Abua/Odual Local Government Area (S1), Alimi community in Elele, Emohua Local Government Area (S2), Asarama, Andoni Local Government Area (S3), Ekata, Ahoada East Local Government Area (S4) and Yege, Khana Local Government Area (S5) in Rivers State, Nigeria. Samples were aseptically collected, and the total heterotrophic bacterial count was enumerated by standard plate count techniques. Bacterial colonies were molecularly characterised by sequencing of the 16S rRNA gene. Synthesis of lipase was screened on tributyrin agar, and quantitative lipase activity was determined by p-nitrophenyl palmitate assay. The results of the study reveal that the piles of oil palm fruits contain a high diversity of metabolically active bacteria able to degrade the lipids. The total number of bacteria in the different collations ranged from (4.0 × 105cfu/g) to (5.7 × 106cfu/g), and the highest was recorded in sample S4, which indicated the growth of microorganisms caused by the local physicochemical circumstances (p < 0.05). Microorganisms identified were: Bacillus cereus (29.5%), Staphylococcus aureus (23.9%), Bacillus subtilis (15.9%), Pseudomonas aeruginosa (15.9%) and Bacillus licheniformis (14.8%). All the isolates were lipolytic with hydrolysis zones of 2.6 cm in B. cereus, 3.5 cm in P. aeruginosa, 2.2 cm in S. aureus, 3.1 cm in B. subtilis and 3.7 cm in B. licheniformis. The highest lipase producer was B. licheniformis (55 µmol/min/ml), followed by P. aeruginosa (48 µmol/min/ml), B. subtilis (40 µmol/min/ml) and B. cereus and S. aureus showed lower activity (24 and 20 µmol/min/ml, respectively). The data support the function of these bacterial communities in lipid degradation and their capacity to adapt to oil-rich environments. The strong potential of B. licheniformis and P. aeruginosa to synthesise lipase suggests that they may be suitable enzymes for commercial enzyme production and for bioremediation of sites contaminated with lipids. Further studies of isolates of Pseudomonas aeruginosa and Bacillus licheniformis exhibiting high lipase activity may have a role to play in the large-scale production of lipase enzymes, and in optimising fermentation conditions.