Market and product

Compiled by Bao Hien

A research team in India has developed a two-stage process combining a deep eutectic solvent (DES) and bacteria to break down waste tire rubber. The approach could offer an additional route for recycling end-of-life tires, complementing existing mechanical and thermal methods.

The study was conducted by Pritish R. Shukla, Utpal Roy and Sunil Bhand of BITS Pilani, India, and published in RSC Advances on May 18, 2026.

The process begins with pretreating ground tire rubber using a DES made from choline chloride and urea. The solvent causes the rubber to swell and helps extract some sulfur-containing and metallic compounds, making the polymer network more accessible to subsequent biological treatment.

The pretreated rubber is then exposed to Rhodococcus rhodochrous RPK1, a bacterial strain cultured for 28 days. The microorganisms use enzymes to break down components of the rubber polymer.

The combined treatment produced more significant changes than either method used alone. The number of viable bacterial cells increased by 43.87% compared with the sample treated biologically without DES pretreatment. Crosslink density fell by 43.6%, compared with 15.81% for biological treatment alone and 26.84% for DES treatment alone.

Analysis of the rubber surface also showed a 46.17% reduction in sulfur content and a 68.45% reduction in zinc content. After 28 days, the combined process resulted in a mass loss of 12.53%, substantially higher than the 1.63% recorded with bacterial treatment alone.

The researchers also observed marked increases in enzyme activity. Laccase and peroxidase activities rose 105.5-fold and 99.5-fold, respectively, compared with their initial levels in the biological control.

Another feature of the process is the potential to recover and reuse the solvent. After filtration, the DES retained some of its eutectic properties and could be used in a second treatment cycle, achieving comparable devulcanization efficiency.

The findings point to a potential chemical-biological route for recovering materials from end-of-life tires. Rather than replacing mechanical grinding or pyrolysis, the approach could complement existing recycling technologies and broaden options for managing waste rubber.

However, the research remains at the laboratory stage. The process achieves partial degradation rather than complete breakdown of the rubber, and further work is needed to optimize the treatment and assess its feasibility at a larger scale.