Enzymatic Hydrolysis of Textile and Cardboard Waste as a Glucose Source for the Production of Limonene in Escherichia coli

Cellulose containing textiles (cotton) and cardboard/carton waste represent a large reservoir of untapped organic carbon. These wastes have enormous potential for use as carbon feedstock in industrial biotechnological processes. Essentially, cotton/cardboard (CC) waste is pure cellulose (with some additives) in the form of polymerised glucose consisting of β-(1→4)-linked D-glucose subunits. One of the largest and most diverse classes of natural chemicals that can be produced from glucose are terpenes with a wide range of applications as flavours, fragrances, pharmaceuticals, biopesticides, and biofuels. Here we have investigated the bioconversion of CC waste into the exemplary terpene limonene as a proof of concept. Six different CC waste streams were enzymatically hydrolysed and used to produce limonene using the Escherichia coli (E. coli) microbial cell factory. The D-glucose content in the CC hydrolysate (glucose juice) was determined and then metabolised by E. coli via a manipulated heterogeneous biolipid synthesis pathway (the mevalonate pathway) to produce limonene. This study represents an important proof of concept for the production of terpenes from hydrolysed CC waste streams.