Enzymatic degumming

Enzyme which can hydrolyse the sericin is classified as proteolytic enzymes [63-65]. The proteolytic enzymes cleave the peptide/amide linkages and convert them into amino acid. Mainly there are three types of proteolytic enzymes such as zinc protease (e.g. carboxy peptidase A), serine protease (Chymotrypsin, Trypsin, Thrombin) and thiol protease (acts as cystine residue in the protein). The function of proteolytic enzymes in their degree of degumming depends on the pH of the bath and the optimum activity is found to be different at different pH for different enzymes. 

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In the enzymatic degumming process, part of the hydratable phosphatides is enzymatically modified by removing the fatty acid on the C-2 position of the glycerol, using a phospholipase A2 enzyme as biocatalyst. These modified phosphatides facilitate the removal of the remaining NHP. Table 4.10 shows the results of an enzymatic degumming... 

Enzymatic degumming is a relatively new process. An enzyme, phospholipase, converts phospholipids into lysophospholipids that can be removed by centrifugation. Crude oil, pretreated with a combination of sodium hydroxide and citric acid, is... 

Enzymatic degumming was first introduced by Lurgi as the EnzyMax technology. " Reduced gum volume due to formation of water-soluble lyso-phosphatide, avoidance of soap stock formation, hence increased oil yield, and reduced environmental impact have made enzymatic degumming based on phospholipase enzyme an alternative to conventional degumming with increasing commercial interest (Figure 9.1.8). ... 

Layout of enzymatic degumming (reproduced with the permission of Novozymes). 

The research showed that optimal processing conditions during the application of laccase preparations for enzymatic degumming of raw hemp fibres required the following conditions ... 

In general, enzymatic degumming minimizes oil retained in the gum, resulting in improved oil yields. The enzymatic hydrolysis reaction typically requires 5-6 hours and utilizes less water than water and acid degumming processes. Reductions in enzyme production costs and enhanced enzyme activity and stability could make enzymatic degumming process very attractive for oil refining industry in the near fumre. 

One to three percent of water is mixed thoroughly with the oil at 50-70 °C. The phospholipids hydrate within 1 hour to form a gum with a higher specific density than the oil. The easily hydratable phospholipids are PC, PI and LPC. PE and PA have low hydrating properties and are therefore marked as nonhydratable phospholipids (NHPs). In practice a mix of these various phospholipids is separated in the lecithin gum. After this water degumming process, sometimes enzymatic degumming is applied for hydrolysing the NHP with phospholipase-A enzymes into hydrophilic lysophosphatidylethanolamine... 

Zheng, L, Du., B. (2009), Neural network modeling for bio-enzymatic degumming on kenaf," 5th International Conference on Natural Computation, JCNC 2009, vol. 2, pp. 223-226... 

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