A green and sustainable technology for the development of artificial protein fibers from sorghum distillers grains for industrialization

Abstract

For the first time, artificial fibers from proteins, mainly kafirin and glutelin, from sorghum distillers grains (SDG) have been developed. SDG is difficult to digest due to dense cystine crosslinkages, therefore, is a poor animal feed with much lower value than corn distillers grains. However, dense cystine crosslinkages are an advantage for fiber properties, such as mechanical properties and wet stability. Also, fibers are much more expensive than feed, hence, can add higher values to sorghum industry. Previously, only kafirin was extracted from SDG using traditional solvents for plant proteins, such as alcohol/water, acetic acid, and formic acid. However, these solvents provided kafirin with poor or no spinnability. Glutelin, another major protein in SDG, about 35% of total, had not been used for industrial applications. We developed a green and sustainable water-based system that dissolved sorghum proteins including both kafirin and glutelin and achieved desirable fiber spinnability. We also developed the green aqueous coagulation and oxidation systems to effectively solidify protein fibers after wet spinning from our aqueous spinning solution and recovered cystine crosslinkages between sorghum protein molecules. The artificial sorghum protein fibers from our total aqueous and green spinning system have mechanical properties better than soy protein fibers and regenerated feather keratin fibers. We also used the sustainable sucrose-derived aldehydes to chemically crosslink sorghum proteins. With only 2% of the crosslinker based on weight of fibers, our artificial sorghum protein fibers have mechanical properties better than that of wool.