Ribbon retting of jute—a prospective and eco-friendly method for improvement of fibre quality

Abstract

Jute—an important cash crop of eastern India is traditionally grown for extraction of fibre by a natural microbial process known as retting. Usually mature stems of harvested jute plants are allowed to ret in pond or ditch water. Retting is a preferential rotting process to separate the fibre from woody stem without damaging the fibre cellulose. Retting microbes consume the non-fibrous cementing materials mainly pectin and hemicellulose. Over retting causes degradation of fibre cellulose while under retting causes incomplete removal of gummy materials viz., pectic substances. Both over retting and under retting which are very difficult to control causes production of low grade jute fibre. In conventional retting, a huge biomass undergoes decomposition in stagnant water, so retting causes environmental pollution. In ribbon retting, ribbons are stripped out mechanically from the stem of mature jute plants, coiled and allowed to ret under water. Ribbon retting reduces time of normal retting by 4–5 days. Moreover, requirement of water for ribbon retting is almost half in comparison to conventional whole plant retting under normal condition. This also reduces environmental pollution to a great extent. But use of efficient pectinolytic microbial inoculum improves quality of fibre, further reduce the time of retting and the environmental pollution. In our study, a mixed bacterial retting culture, developed in our institute, was inoculated during ribbon retting of jute. The ribbon retted jute fibres are absolutely free from bark and were of higher grade. Moreover, the fibre filaments were stronger, improved coloured and finer textured compared to conventional stem retted jute fibres. Most of the defects arising from conventional retting could be overcome by ribbon retting. So, ribbon retting is a great promise to produce high quality jute fibre in one hand and a more eco-friendly measure on the other.