Biodesulfurization of vulcanized rubber by enzymes induced from Gordonia amicalisa

Devulcanization of natural rubber vulcanizates by Bacillus cereus TISTR 2651

“…A decrease in the peak intensities of S-C (at 162.7 eV) and S-S (at 164.2 eV) were clearly observed, while the peak of the S-O bond appeared at 166.8 eV (Figure 4) [42]. This result supported that B. cereus TISTR 2651 causes the oxidation of sulfide crosslinks and that the sulfur may be converted to oxygen-containing sulfur-based groups [21]. Accordingly, the enzymes in the microorganism can catalyze the oxidation reaction, and the desulfurization pathway of B. cereus TISTR 2651 was proposed to be analogous to the 4S pathway as described in Figure 5 [24,30,31].…”

“…After devulcanization for 20 days, a peak at 1088 cm -1 (S=O stretching) was formed and the intensity of the peak at 1540 cm -1 was substantially diminished. This result suggested that B. cereus TISTR 2651 not only ruptured the partial main chains of rubber molecules but also oxidized the sulfide crosslinks via some metabolic pathway [21,41]. Additionally, the band located at 1662 cm -1 (C=C deformations) had the high intensity in the devulcanized sample.…”

“…Before devulcanization, the characteristic bands of cis-1,4polyisoprene were observed at 2960-2850 cm -1 , attributed to the C-H saturated stretching [35]. The bands located at 1662 cm -1 were assigned to C=C deformations [21]. The stretching frequency of methyl-assisted conjugated double bonds due to a reversion was observed at 1540 cm -1 [36][37][38].…”

“…Recycling of the vulcanized rubber is an alternative method that converts the rubber waste into value added products [5][6][7]. Devulcanization is one form of recycling, where the crosslinked bonds in the rubber chains are cleaved, and can be classified into the three broad processes of physical [8][9][10][11][12][13][14], chemical [12,13,[15][16][17][18][19][20] and biological [12,[21][22][23][24][25][26][27][28][29] devulcanization processes. Physical devulcanization generally requires a high temperature or external energy for cleavage of the crosslinked bonds and so this process has a high cost and high energy consumption, challenging its economic and environmental viability.…”

“…Several studies have confirmed that biological devulcanization is a potentially viable method to break sulfide crosslinks using selective microorganisms via various metabolic pathways [22-24, 30, 31]. The effect of Gordonia amicalisa on biological devulcanization of vulcanized synthetic rubber (vulcanized isoprene and vulcanized styrene butadiene rubber) was investigated [21]. The vulcanized styrene butadiene rubber was the specific substrate that could induce G. amicalisa to release desulfurizing enzyme on the devulcanization process [21].…”