4. Conclusions
It is clear from this study and other published works that low specific growth rate control feeding consistently helped to enhance the production of extracellular microbial lipase in HCDF.This is irrespective of the nature of the immiscible substrate used for growth and lipase production i.e., either a pure fatty acid such as oleic acid or whole plant oil such as palm oil. The exact reason behind the increased lipase production when this specific feeding mode was used in HCDF is unclear at this stage. It is suggested that a more detailed study using tools such as proteomics analysis may provide better explanation for the observed effect.
In addition to the substrate feeding mode being relatively simpler to implement, the use of refined palm oil as an alternative carbon substrate to oleic acid proved effective for microbial lipase production. Moreover, using palm oil as the sole substrate obviated the need for chemical antifoams in the production of lipase. Overhead costs of producing lipase could be made to be very competitive when the fermentation facilities are in close proximity of the oil palm plantation in addition to leveraging on the existing palm oil mill infrastructure.