In this study, hydrothermal acid treatment for efficient recovery of sugar from Golenkinia sp. was investigated. The initial glucose and XMG (xylose, mannose, and galactose) contents of a prepared Golenkinia sp. solution (40 g/L) were 15.05 and 5.24 g/L, respectively. The microalgal cell walls were hydrolyzed, for sugar recovery, by enzymatic saccharification and/or hydrothermal acid treatment. Among the various hydrothermal acid treatment conditions, the most optimal were the 2.0% H2SO4 concentration at 150 degrees C for 15 min, under which the glucose-and XMG-extraction yields were 71.7% and 64.9%, respectively. By pH 4.8, 50 degrees C enzymatic hydrolysis after optimal hydrothermal acid treatment, the glucose-and XMG-extraction yields were additionally increased by 8.3% and 0.8%, respectively. After hydrothermal acid treatment, the combination with the enzymatic hydrolysis process improved the total sugar yield of Golenkinia sp. to 75.4%. (C) 2015 Elsevier Ltd. All rights reserved.