LAUSR

This study evaluated the use of biomass of Chlorella minutissima grown in 40-L photobioreactors using a Guillard f/2 biomass at over 80% moisture content as feedstock to produce ethyl esters. The study design investigated the influence of acid catalyst type (HCl or H 2 SO 4 ) and concentration (0.3 or 0.6 mol L −1 ), co-solvent to ethanol ratio (1:10 or 1:5 v/v), and acyl acceptor to biomass ratio (25 mL g −1 or 50 mL g −1 ) on ester yield and conversion. An L 8 Taguchi design was used to evaluate the influence of the factors, demonstrating a range of conversion ranging from 37 to 98%. Furthermore, the effects of reaction conditions on the residual biomass were assessed by measuring the concentration of acid-labile carbohydrates, which could be utilized in integrated sugar- and lipid-based algal refineries. It was found that in situ transesterification using HCl can provide easily accessible and fermentable carbohydrates at concentrations of about 32 wt% in residual biomass. In this sense, the findings of this study demonstrate a further step in the integration of microalgae biomass in the development of liquid-fuel biorefineries. Graphical abstract