Compositions and methods of making a culture medium from a polymeric material are described herein. The method can include (a) depolymerizing and/or dispersing the polymeric material to obtain a depolymerized and/or dispersed residue, and (b) combining the depolymerized and/or dispersed residue with one or more adjuvants to form a culture medium. In some embodiments, the polymeric material can be a plastic article, such as a waste carpet material. Culture media prepared from the compositions and methods are also described. The culture media are suitable for culturing microorganisms including bacterium, algae, and fungus. The microorganisms can be used to produce a bioproduct such as a biopolymer, an enzyme, or a cellular metabolite.