Fermented Soymeals and Their Reactive Blends with Poly(butylene adipate-co-terephthalate) in Engineering Biodegradable Cast Films for Sustainable Packaging

The main goal of this research was to utilize an inexpensive soymeal (SM) rather than an expensive purified soy protein isolate and soy protein concentrate for biobased and biodegradable sustainable film development. Green processing approaches of soymeal, with the aim of destructurizing its carbohydrates that are deterrent to plastic making, were conducted. This process involves natural fermentation (NF), yeast fermentation (YF), and simultaneous enzyme saccharification and fermentation (YEF). Soymeals treated as such were then plasticized with glycerol and blended with poly(butylene adipate-co-terephthalate) (PBAT). Compatibilization of the fermentation treated and plasticized soymeal with PBAT was also conducted via reactive extrusion. The resulting blended materials were then extrusion tasted to produce films of 0.35 mm thickness. The performance of the film, including mechanical, thermal, morphology, and water resistance as a function of the fermentation treatments, and compatibilization were evaluated. Composition analysis and a morphology study showed that YEF provided better destructurization of carbohydrates leaving behind a protein rich residue that was used for film making. Consistent with this observation, the YEFSM-PBAT blend films exhibited better tensile properties, thermal stability, and moisture resistance. Also, significant improvements in tensile strength, water resistance, and thermal stability of the films were achieved as a result of the compatibilization of PBAT with the plasticized protein meals. Fermentation of soymeal was found to be an effective and inexpensive method of destructurizing unnecessary carbohydrates for plastic production without the use of any toxic chemicals or extraction techniques. These results can be extended to other protein rich biomasses such as canola meal and corn meal. The developed blend films showed promising performance with several potential biodegradable applications including consumer bags, packaging film, agricultural mulch film, and silage wraps.