(475i) Enzymatic Polymerization of Natural Phenolic Lipids and Their Potential Application as Anti-Biofouling Materials

Biofouling is caused by a wide range of living organisms, such as bacteria, macroalgae, or other water-born organisms such as corals, hydroids, and barnacles. These micro- and macro-organisms attach to the solid surface and colonize it, resulting in the formation of a biofilm. Biofouling causes various persistent problems in industry, medical, dental, and public health, and is difficult to prevent and remove. Biofouling is initiated by the adhesion of microbes to solid surfaces, and with subsequent production of extracellular polymers (in brief, exopolymers) a biofilm is formed. Therefore an effective antibiofouling material should prevent both cell adhesion and biofilm formation on the surfaces.

Although there have been some antibiofouling materials and methods developed over the years, no plausible results have been found. Many antibiofouling materials were rendered ineffective due to the decrease of activity with time, inability to penetrate the biofilm and adverse effects on environment. Also, most of the methods developed for controlling biofilms are either costly or have environmental problems. Therefore a cost effective antibiofouling material must be developed in an environmentally friendly way. In this research, natural phenolic lipids are used as a precursor for developing a set of novel antibiofouling materials which can prevent cell adhesion and biofilm formation. We have used cashew nut shell liquid (CNSL), a byproduct of the cashew industry, which is rich in phenolic lipids as a starting material.

Oxidative enzymatic synthesis was used to polymerize the phenolic lipids. Recently enzymatic polymerization has gained importance as a new method of polymer synthesis. New polymeric materials which are difficult to be obtained by conventional methods can be obtained by using enzymes in an environmentally friendly way. The polymerization of the phenolic lipids proceeded in the presence of an organic solvent: buffer system with soybean peroxidase and H2O2 being added as an oxidizing agent. The polymer structure was characterized by NMR and FTIR spectroscopy. The polymers obtained were then cured in the presence of cobalt napthanate and MEKP to give a glossy film on a solid surface. The curing of the polymer was monitored by FTIR spectroscopy and the hardness of the film was tested using a pencil scratch hardness test.

The organic coatings obtained were then tested for their antibiofouling characteristics in the presence of Gram- positive and negative bacteria. The biofilm formation and the cell adhesion (live/dead cell analysis) to the surfaces have been monitored by scanning electron microscopy (SEM) and epifluoroscent microscopy. The bacteria were grown on the un-coated slides and coated slides for 15 days with the growth media replaced every 48 hrs. The coated slides showed significant antibiofouling properties resisting both cell adhesion and biofilm formation. Furthermore, the coated slides maintained significant antibiofouling activity even after 15 days, which indicated that the functional groups responsible for the antibiofouling effect are not depleted or diffusive. The biofilm coverage area on a surface has been quantified using J image analysis software. Consequently, the enzymatic polymerization mechanisms of natural phenolic lipids from CNSL and their potential function as novel antibiofouling materials is discussed in this project.