# Enzymatic Degumming of Soybean Oil for Raw Material Preparation in BioFuel Production
## 4 Discussion
The components of biofuel meet the necessary characteristics for use in diesel engines. The high proportion of FAME provides good compatibility with internal combustion engines, improves the combustion process, and contributes to the reduction of emissions of harmful substances. Thus, the obtained biofuel fraction is a promising source of environmentally friendly energy, characterized by high operational properties. The FTIR spectra of crude soybean oil, degummed soybean oil, and biofuel were nearly similar, and no significant difference were observed as shown in Figures 7 and 8. The identification of functional groups and bands corresponding to different stretching and bending vibrations clearly indicates the corresponding characteristic bands of the expected functional groups. Figure 5: Chromatogram of transesterification products. Figure 8: FTIR spectra of crude soybean oil, degummed soybean oil and transesterification products in the region 1500 to 400 cm\({}^{-1}\). Figure 6: Mass spectrum of the fraction with retention time 8.814 min (**top**) and library (reference) mass spectrum of (Z)-9-octadecenoic acid methyl ester (**bottom**). Figure 7: FTIR spectra of crude soybean oil, degummed soybean oil, and transesterification products. According to the FTIR spectrum, the band at 3475 cm\({}^{-1}\) represents the O-H stretching vibrations in crude soybean oil and degummed soybean oil. The absorption band shifted at 3464 cm\({}^{-1}\) in biofuels is attributed to O-H stretching vibrations, which confirm the lower polarity in the absence of phospholipid groups. In all three spectra, the band at 3009 cm\({}^{-1}\) represents the C=C-H stretching vibrations of the cis double bond of unsaturation, while the bands at 2922 and 2853 cm\({}^{-1}\) are characteristics of the asymmetric and symmetric vibrations of the hydrocarbon chain -CH\({}_{2}\) in the aliphatic fatty acid. Asymmetric stretching vibrations of the -CH\({}_{3}\) group at 1435 and 1361 cm\({}^{-1}\) increased in the biofuel spectrum, indicating a change in the phospholipid group to methyl. In oils, the ester carbonyl (C=O) functional group shows a characteristic stretching band of triglyceride at 1743 cm\({}^{-1}\). In biofuel, this band shifted to 1741 cm\({}^{-1}\), indicating the absence of a polar phospholipid group. In all spectra, bending vibrations of -CH\({}_{2}\) scissoring aliphatic groups were observed at 1463-1455 cm\({}^{-1}\). The strongest evidence of transesterification is the appearance of new signals at 1435 and 1361 cm\({}^{-1}\), which are certainly asymmetric and symmetric bending vibrations of the CH\({}_{3}\) group methyl ester. Another visible transformation is in the ester control signal area at approximately 1241 cm\({}^{-1}\). The broad and strong signal at 1160 cm\({}^{-1}\) in oils will separate into two specific signals at 1195 and 1169 cm\({}^{-1}\) in biofuel. The averaging of the energy over the triple ester group of the triglycerides is gone. The broad signal in all spectra at 719 cm\({}^{-1}\) is due to overlapping the CH\({}_{2}\) rocking vibration and the out-of-plane vibration of cis-disubstituted olefins (Figure 8). The variability of the vibrational frequency values of the same functional groups listed in Table 8 (in particular -CH\({}_{2}\), C-O, P=O, P-O) is due to changes in their chemical environment resulting from enzymatic degumming and further transesterification. The change in the structure of the samples affects the electron density around the corresponding atoms, the polarity of chemical bonds, and the strength of hydrogen bonding and dipole interactions, which, in turn, leads to a slight shift of the absorption bands in the IR spectra. Thus, the presence of different frequencies for the same types of vibrations is an expected consequence of the chemical modification of the system during the processing and serves as additional confirmation of structural changes in the samples.