Development of green methodologies in the chemical investigation of agro-industrial wastes of sugar cane

Abstract

Sugarcane (Saccharum spp) is grown in more than 100 countries. Despite this worldwide diffusion, around 80% of production is concentrated in ten countries, with Brazil being the world's largest producer (655.2 million tons in the 2015/2016 harvest). Sugar and ethanol obtained by fermentation are the two main products obtained from this raw material. Brazil is responsible for more than half of the sugar sold in the world, producing about 37.3 million tons of the product in the 2015/2016 season and the second largest producer of ethanol with an estimated production of 28.5 billion liters. 1 As a consequence, annually, more than 400 million tons of sugarcane waste (straw, leaves and bagasse) are generated annually in the manufacture of these two products. Although they are often burned for the production of steam and electricity in mills, and important quantities of straw are left in the field to maintain soil nutrient balance, these residues together with those generated during the fermentation process itself (such as filter cake , for example), could be used to obtain higher added-value chemical products and additives. Cavalheiro and colleagues investigated the chemical composition of the leaves of different sugarcane genotypes by HPLC-PDA / UV, HPLC-PDA / UV-MS and NMR, observing the presence of 144 metabolites, with special emphasis on C flavone isomers glycosides, such as luteolin-8-C-glucoside, which has known antifungal activity, and apigenin-8-C-arabinosyl-6-C-glucoside, diosmetine-8-C-glycoside and apigenin-6-C-glucoside. The authors conclude that these compounds could enable a better use of waste generated in the production of ethanol and sugar, adding value to the production chain of such products, since flavonoids of this nature (C-glycosylates) are rarer in nature and many are not commercially available. In addition, triterpenes and phenolic acids have also been described in leaves of sugarcane. Thus, the objective of the proposal is to investigate the presence of these and other organic compounds in residues from the crop and the processing of sugar cane. Extractions with different techniques in green extracting media (including Natural Deep Eutectic Solvents, having as one of its components the sucrose itself), as well as methods by ultra-high performance liquid chromatography (UHPLC) will be optimized statistically. The constituents of the extracts will be identified and quantified in mixture by UHPLC coupled to mass spectrometry and, if necessary, by Nuclear Magnetic Resonance. (AU)