D-Lactic acid production from Cistus ladanifer residues: Co-fermentation of pentoses and hexoses by Escherichia coli JU15

In this study, glucan-rich solids, and xylose-rich hydrolysates obtained from Cistus ladanifer distillery residues (CLR) were used for d-lactic acid (d-LA) production by the d-lactogenic Escherichia coli strain JU15. Firstly, hemicellulosic autohydrolysis process submitted to dilute sulfuric acid-catalysed post-hydrolysis. The influence of operational conditions on oligosaccharides hydrolysis was assessed combined severity parameter (CS) in range 1.1–2.3. optimum post-hydrolysis found CS 1.6 (300 mM H2SO4, 15 min, 121 °C). Subsequent detoxification procedures post hydrolysed liquors carried out, where 9.1% (w/v) powdered activated charcoal enabled a full removal furfural, 5-hydroxymethylfurfural (HMF), phenolic compounds together with reduction acetic (37%), formic (27%). Diverse fermentation modes using detoxified non-detoxified hydrolysates, as well previously NaOH delignified solids alone (SHF or SSF) pentoses (SSCF) (5% loading) performed. For all tested conditions, both hemicellulose- cellulose-derived sugars can be efficiently carbon source produce E. JU15 d-LA yield always surpassing 92 gd-LA/100 g sugars.