A Study of Bacteria Isolates from Gin Trash for Cotton Fibre Wax removal during Bio Scouring

Abstract

Alkaline pectinase scoured cotton fibres show low absorbency levels. Thisis mainly due to the inability of the enzyme to remove cotton wax concurrently with the other impurities. The enzyme requires temperature of up to 50°C for activity while cotton fibre wax requires temperatures of 75-100 o C to melt, at which the pectinase would be denatured. This research therefore identified the need to use cotton fibre wax degrading microbial isolates at mutually favorable temperatures, pH and incubation time to enhance the wax removal during bio scouring. The main objective was to investigate the role of the bacteria isolates from gin trash in cotton fibre wax biodegradation during the bio scouring process. Bacteria cultures were grown and isolated from cotton gin trashes collected from Kibos and Kitui ginneries as case studies. All the three pure isolates,yellow, white and blue obtained were found to have activity on paraffin wax at 37 0 Cto 45 0 C.Universal Rotatable Design (URD) was used to design the optimized process parameters during cotton wax removal by the isolates. Wax removal efficiency was then assessed by the percentage weight loss after solvent extraction of the treated fibres. Maximumwax of 0.765% out of 1.2% present in the fibres was removed at 45°C, pH 8 within 1 hour. Asecond-order polynomial regression model was fittedand found adequate with a determination coefficient, R 2 ,of 0.94032 (p < 0.005). Minitab 15, Monte Carlos and SPSS statistical tools were used for the parameters modelling and sensitivity analysis.Temperature was found to be the most significant variable in the bacterial cotton wax removal. At 45 °C, pH 8, maximum 0.747%wax was removed by the bacteria with pectinase treatment within 1 hour. This amount was comparable to the 0.72% and 0.844% wax removed by caustic and pectinase with surfactants scour procedures. The isolates treated cotton fibres showed a slight3% increase in strength. Key words: Gin trash; Bacteria isolates;pectinase removal;Optimization; Modeling parameters sensitivity. enzyme; cotton wax