Corn steep liquor as a secondary raw material for direct sourcing of gramicidin

Gramicidin is a group of peptide antibiotics with many applications in the pharmaceutical and agrochemical industries. This antibiotic can be extracted from Aneurinibacillus aneurinilyticus, belonged to the Bacillus aneurinolyticus cluster (Shida et al., 1996), that can grow spontaneously in a residual stream of corn wet-milling industry, called also corn steep liquor (CSL). Gramicidin is produced industrially by controlled fermentation with a higher production cost, as it is a secondary metabolite. Nevertheless, the extraction of the antibiotic from the low-cost residual stream can be profitable, reducing the costs and promoting circular economy. It has been shown, that Gramicidin can be linked to the biosurfactant surfactin, obtaining Gramicidin-surfactin heteropolymers with higher molecular weight (Rautenbach et al., 2017). López-Prieto et al. López-Prieto et al. (2021) also confirmed the presence of Gramicidin S in a cell-bound biosurfactant extract obtained from a synthetic medium inoculated by Aneurinibacillus aneurinilyticus. The findings of this preliminary research required new experiments making use of CSL as a nutrient source. In the current work, Gramicidin was extracted from CSL following the procedure described in patent (ES 2795574B2). The extract was analyzed by electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) with time-of-flight (TOF) analyzer, corroborating the presence of Gramicidin in CSL. Fig. 1 includes a picture of the extract obtained from CSL containing Gramicidin. This is the first time that it is contemplated the evaluation of CSL as a source of Gramicidin. It is proposed the use of a residual stream to obtain the antibiotic preventing the use of non-renewable raw materials. Further experiments are required to advance knowledge about application of Gramicidin's extraction at industrial scale.