Process optimization of the extraction of reducing sugars and total phenolic compounds from the invasive alga Rugulopteryx okamurae by response surface methodology (RSM)

Abstract

The brown marine alga Rugulopteryx okamurae (R. okamurae) has quickly spread through the Mediterranean coasts since it was firstly spotted in the area in 2015. This alien species has already colonized a great part of the Mediterranean western coasts and displaced the local biota, disrupting the natural and autochthonous marine ecosystem. Moreover, the related ‘green’ tides also provoke environmental problems ashore that need to be addressed. Comprehending the potential of this unwanted biomass could be of vital importance to lessen its ecological impact. In this study, the ashore R. okamurae was assessed for its potential as raw material for the extraction of reducing sugars and polyphenolic compounds with antioxidant capacities. The extraction process was evaluated and optimized using the response to surface methodology (RSM) combined with a modified Box-Behnken design. Initially, 2 key operational factors were identified as the most influential parameters (i.e. drying temperature and milling time). However, the type of solvent and the use of zeolite were included in the design as factors that potentially could have a significant impact on the process. The analyzed responses were the extraction yields for total phenolic compounds (TPC) and reducing sugars (RS). For the extraction of TPC the optimized methodology was based on the use of ethanol as solvent, a drying temperature of 60 °C and a zeolite-assisted milling time of 60 s, reaching a maximum yield of 15.33 ggallic acid kg−1. For the extraction of RS the optimized methodology was based on the use of water as solvent, a drying temperature of 100 °C and a zeolite-absence milling time of 50s, reaching a maximum yield of 10.42 gglucose kg−1.