Retting and Degumming of Flax Using Biotechnology Eco-friendly Approach

Flax retting is a treatment process employed to dissolve or rot away much of the cellular tissues and pectins surrounding bast/fiber bundles thus facilitating separation of the fiber from the stem. The microbial retting is one of the most environmentally friendly process. The rich source of microbes contributing to flax retting is the retting water in commercial retting plants. The main objective of this work is to accelerate the flax retting using selected bacterial strains contributing to retting and degumming of flax in order to avoid chemicals causing environmental pollution. In this work, reuse of retting water for acceleration of flax retting was tested. The results show that, the reuse of retted water in new cycle of flax retting has accelerated the retting completion by 8.3-25% depending on the ratio of reused retted water in the retting liquor. Therefore, samples of flax straw retted water and soils from flax fields located in Nile Valley and Delta soils were collected for isolation of flax retting bacteria predominant in the retting effluents. Identification of the isolates was done using morphological, physiological and biochemical tests. Ten bacterial isolates were identified as Lactococcus cremoris, Chryseobacterium culicis, Serratia marcescens, Capnocytophage granulose, Micrococcus luteus, Enterobacter homraechei, Klebsiella oxytoca, Paenibacillus polymyxa, Proteus mirabilis and Bacillus humi. Three efficient strains in pectinase production necessary for flax retting were selected to test their role in enhancing the retting process. These strains are Bacillus humi, Chryseobacterium culicis and Micrococcus luteus which showed specific pectinase activity 37.17, 33.53 and 28 Umg(1) respectively. The effect of these strains on retting duration and fiber quality were studied. The combinations of the three strains were tested in the lab scale cylindrical experimental bioreactor and each of the combinations was compared with the classical retting process of the industrial units. The combined treatment using strains: Chryseobacterium culicis, Micrococcus luteus and Bacillus humi resulted in the reduction of the retting duration by 30%, whereas, the mixed inocula containing Chryseobacterium culicis and Micrococcusluteus reduced the retting time by 25%. The mixture of Micrococcus luteus and Bacillus humi reduced the retting duration by 20%. The determination of weight loss, tensile strength, whiteness and yellowness of the fibers after microbial retting was monitored. These results indicate that the obtained specific bacterial strains enhanced the retting process.