Detoxification and fermentation of dissolved colored discarded cotton fabrics

Authors: Klasson, K Thomas; FARRELL, MATTHEW - Cotton, Inc

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 4/25/2022
Publication Date: 5/1/2022
Citation: Klasson, K.T., Farrell, M.J. 2022. Detoxification and fermentation of dissolved colored discarded cotton fabrics. In: Proceedings of the National Cotton Council Beltwide Cotton Conferences, January 4-6, 2022, San Antonio, Texas. p. 712-716.

Interpretive Summary: U.S. Department of Energy has evaluated biomass as a good source of material for conversion to simple sugars followed by fermentation to fuels and chemicals. Cotton, in discarded dyed fabric materials, is composed of significant quantities of bound sugars in the form of cellulose which can be converted into sugars. However, the dyes in the discarded cotton products can be toxic to microorganisms used in fermentation. Therefore, our intention was to develop a method that removes these compounds before fermentation. Results show that powdered activated carbon was effective in removing a significant portion of the dyes from the solubilized dyed cotton fabrics; in some cases, 75% was removed. Fermentation of the sugars used two bacteria: One bacterium for anaerobic fermentation to acetone/butanol/ethanol and another bacterium for for aerobic fermentation to acetoin. We showed that the activated carbon treatment improved fermentation in the case of acetone/butanol/ethanol over untreated controls. In the case of acetoin, the results were not as conclusive and suggested that the bacterium used may have a higher tolerance to the compounds (dyes) and may not require activated carbons treatment, when solubilized textiles are used in acetoin fermentation.

Technical Abstract: U.S. Department of Energy has evaluated lignocellulosic biomass as a viable source of material for conversion (i.e., hydrolysis) to simple sugars followed by microbial fermentation to fuels and chemicals. Cotton, in discarded dyed fabric materials, is composed of significant quantities of polymeric sugars in the form of cellulose which can be converted into sugars by the same type of hydrolysis process. However, in addition to the dyes in the discarded cotton products, the conversion process often generates chemical byproducts that are toxic or partially inhibitory to microorganisms. Therefore, our intention was to develop a robust technology that removes these inhibitors prior to fermentation. Results show that powdered activated carbon was effective in removing a significant portion of the dyes (as measured by color reduction) from the hydrolyzed (i.e., solubilized) dyed cotton fabrics; in some cases, 75% was removed. Fermentation of the sugars using two bacterial strains, Clostridium beijerinckii for anaerobic fermentation to acetone/butanol/ethanol and Bacillus subtilis for aerobic fermentation to acetoin, showed that the activated carbon treatment improved fermentation yields in the case of C. beijerinckii over untreated controls. In the case of B. subtilis, the results were not as conclusive and suggested that B. subtilis may have a higher tolerance to the inhibitors and may not require activated carbons treatment of textile hydrolysates before being used as a carbon source for fermentation.