A simple, rapid and cost-effective process for production of latex clearing protein to produce oligopolyisoprene molecules

Abstract

Aiming at finding feasible alternatives for rubber waste disposal, the partial enzymatic degradation of poly(cis-1,4-isoprene)-containing materials represents a potential solution. The use of rubber-degrading enzymes and the biotransformation of rubber into new materials is limited by the high costs associated with the production and purification of the enzyme and the complexity of the process. This study presents a simple and low-cost procedure to obtain purified latex clearing protein (Lcp), an enzyme capable of cleaving the double bonds of poly(cis-1,4-isoprene) in presence of oxygen to produce different size of oligomers with terminal aldehyde and ketone groups, respectively. The gene coding for Lcp1VH2 from Gordonia polyisoprenivorans strain VH2 was overexpressed in Escherichia coli C41 (DE3), and by using an auto-induction medium high protein yields were obtained. The cultivation process was described and compared with an IPTG-inducible medium previously used. Purification of the enzyme was performed using salting out precipitation with ammonium sulfate. Different salt concentrations and pH were tested in order to find the optimal for purification, obtaining a concentration of 60mg Lcp per l. The enzymatic activity of the purified enzyme was measured by an oxygen consumption assay in the presence of polyisoprene latex. Volumetric activities of 0.16Uml−1 were obtained at optimal conditions of temperature and pH. The results showed an active and partial purified fraction of Lcp1VH2, able to cleave the backbone of poly(cis-1,4-isoprene) and to produce degradation products that were identified with staining methodologies (Schiff reagent for aldehyde groups and 2,4-DNPH for carbonyl groups) and characterized using nuclear magnetic resonance (NMR). Thirteen different storage conditions were tested for the purified enzyme analyzing the enzymatic activity after 1 and 3 months. Lcp1VH2, as an ammonium sulfate precipitate, was stable, easy to handle and sufficiently active for further analysis. The described methodology offers the possibility to upscale the process and to produce large amounts of this protein.