Production of Bio-ethylene From Wastes of Microalgae to Biodiesel Biorefinery

This work shows the valorization of marine microalgae protein wastes (MMPW), generated from biodiesel production, by obtaining a substrate that can be metabolized for ethylene production. MMPW were hydrolyzed with H2SO4 diluted to get both sugars and amino acids. This hydrolyzate was adapted for the growth of Pseudomonas savastanoi pv. glycinea. Reducing sugars, soluble protein, elemental analysis and gross analysis allowed determining the critical carbon-to-nitrogen ratio, which are associated to maximum specific growth rate, mu(max). A chemically defined medium (CDM) was designed and optimized by using the collected information from fifty-two fermentations with different glucose, glutamate, NaCl, ferrous sulphate, minerals and stirring rotational speed. It was obtained a function that relates the carbon to nitrogen ratio with mu(max) for ethylene production. For C/N=1.25, ethylene production and mu(max) were 15 mu mol ethylene per Dry Cell Weight (DCW), and 0.151h(-1), respectively. However, when the C/N ratio increased to 28, these values were 140 mu mol ethylene g DCW-1 and 0.421h(-1). The methodology proposed in this work will permit to design and evaluate others substrates of raw waste biomass for the production of ethylene.