In vitro studies on the degradation of poly( cis ‐1,4‐isoprene)

Cleavage of the backbone of poly( cis ‐1,4‐isoprene) (IR) in solid rubber material was accomplished by the addition of partially purified latex clearing protein (Lcp1 VH2 ) using a 200‐mL enzyme reactor. Two strategies for the addition of Lcp1 VH2 were studied revealing that the daily addition of 50 µg mL −1 of Lcp1 VH2 for 5 days was clearly a more efficient regime in comparison to a one‐time addition of 250 µg of Lcp1 VH2 at the beginning. Soluble oligo( cis ‐1,4‐isoprene) molecules occurred as degradation products and were identified by ESI‐MS and GPC. Oxygenase activity of Lcp1 VH2 with solid IR particles as substrate was shown for the first time by measuring the oxygen consumption in the reaction medium. A strong decrease of the dissolved oxygen concentration was detected at the end of the assay, which indicates an increase in the number of cleavage reactions. The oligo( cis ‐1,4‐isoprene) molecules comprised 1 to 11 isoprene units and exhibited an average molecular weight ( M n ) of 885 g mol −1 . Isolation of the oligo( cis ‐1,4‐isoprene) molecules was achieved by using silica gel column chromatography. The relative quantification of the isolated products was performed by HPLC‐MS after derivatization with 2,4‐dinitrophenilhydrazyne yielding a concentration of total degradation products of 1.62 g L −1 . Analysis of the polymer surface in samples incubated for 3 days with Lcp1 VH2 via ATR‐FTIR indicated the presence of carbonyl groups, which occurred upon the cleavage reaction. This study presents a cell‐free bioprocess as an alternative rubber treatment that can be applied for the partial degradation of the polymer.