NIRJAFT


DRY RETTING USING FUNGAL CULTURE


Anaerobic bacteria and aerobic microorganisms mostly mediate conventional retting of jute. Complete removal of pectin and polysaccharide gummy materials are necessary to obtain good quality fibre keeping the natural strength of cellulose. For conventional retting of jute, water requirement is 1:20 to get good quality fibre. The crisis of water becomes more severe due to drought situation or late onset of monsoon.


NIRJAFT initiating a research work on retting by the alternate microbial process having the same enzyme activity in aerobic condition. By enrichment culture, some suitable fungi like Aspergillus niger, Aspergillus tamarii, Aspergillus flavus and Sporotrichum thermophile have chosen from the isolated fungi for dry retting of jute. Mother culture was prepared by growing the fungi on potato-dextrose broth.

The fungi were grown on presterilised wheat bran and rice husk mixture in double polypropylene packets.

Full growth of the fungi with complete sporulation was obtained within 10 days incubation at 32 - 40°C. They were used as fungal culture for dry retting of jute. Jute plants of different age from 90 to 130 days old was taken, defoliated and just moistened. The fungal cultures were mixed with sufficient water to make slurry and then applied on defoliated jute plants. The plants were made into bundles and tied with coconut or nylon ropes and then wrapped with polyethene sheets and incubated on bamboo racks for fungal retting.

The Aspergillus function well at normal ambient temperature around 34°C but Sporotrichum thermophille preferred higher temperature for best performance. Growth of fungi on jute plants were checked every alternate day until fibres are loosened and come out easily for extraction. After complete fungal growth the stems are taken out and ribbons are separated by hand. The fungal retted ribbons are then washed gently in water to separate the fibres and dried in air. This dry retting process took 9-10 days. The strength, fineness, colour and lusture of the fibre is highly satisfactory. Instead of acidic intermediate producing mechanistic pathway it ferments in different pathway forming alkaline residue. So this retting procedure may be regarded as a green technology besides water saving. This method has been considered as alternative retting process since, it is fast, requires minimum quantity of water, produces lusturous fibre with natural colour, good strength and fineness and overall absolutely pollution free method. There is no production of obnoxious smelling gas and the farmers need not face the hazard of washing fibres in dirty water and unhealthy condition.