In this work, three residues from the food industry (coconut husk, defatted grape seed and pressed palm fiber) were subjected to subcritical water hydrolysis with the aim of producing fermentable sugars. Hydrolysis kinetics were determined using a semi-batch unit equipped with a 50 mL reactor. The process was conducted at 208 C and 257 C for 30 min, with water flow rate of 33 mL/min and under 20 MPa. The liquefaction degree of the raw materials increased with temperature. The total reducing sugars recovered also increased with temperature. Maximum total reducing sugars recovered for coconut husk, defatted grape seed and pressed palm fiber using SWH were 11.7%, 6.4% and 11.9% from total raw material, respectively. Coconut husk presented the highest amount of monosaccharides (3.4%), followed by pressed palm fiber (2.4%) and defatted grape seeds (0.7%). On the other hand, the degradation products that are also fermentation inhibitors increased with temperature as well. Each raw material presented a different monosaccharides and inhibitors profile, which indicates that SWH should be evaluated and optimized individually for each case. © 2014 Elsevier B.V.89 8998McKendry, P., Energy production from biomass (part 1): Overview of biomass (2002) Bioresource Technology, 83 (1), pp. 37-46. , DOI 10.1016/S0960-8524(01)00118-3, PII S0960852401001183Mirza, U.K., Ahmad, N., Majeed, T., An overview of biomass energy utilization in Pakistan (2008) Renewable and Sustainable Energy Reviews, 12 (7), pp. 1988-1996. , DOI 10.1016/j.rser.2007.04.001, PII S1364032107000494Demirbas, A., Biomass resource facilities and biomass conversion processing for fuels and chemicals (2001) Energy Conversion and Management, 42 (11), pp. 1357-1378. , DOI 10.1016/S0196-8904(00)00137-0, PII S0196890400001370Haghighat Khajavi, S., Kimura, Y., Oomori, T., Matsuno, R., Adachi, S., Kinetics on sucrose decomposition in subcritical water (2005) LWT - Food Science and Technology, 38 (3), pp. 297-302. , DOI 10.1016/j.lwt.2004.06.005, PII S0023643804001550Cheng, L., Ye, X.P., He, R., Liu, S., Investigation of rapid conversion of switchgrass in subcritical water (2009) Fuel Processing Technology, 90, pp. 301-311Brunner, G., Near critical and supercritical water. Part I. Hydrolytic and hydrothermal processes (2009) J. Supercritical Fluids, 47, pp. 373-381Rostagno, M.A., Prado, J.M., Mudhoo, A., Santos, D.T., Forster-Carneiro, T., Meireles, M.A.A., Subcritical and supercritical technology for the production of second generation bioethanol (2014) Critical Reviews in Biotechnology, , in pressYu, Y., Lou, X., Wu, H., Some recent advances in hydrolysis of biomass in hot-compressed water and its comparisons with other hydrolysis methods (2008) Energy and Fuels, 22 (1), pp. 46-60. , DOI 10.1021/ef700292pNegro, M.J., Manzanares, P., Ballesteros, I., Oliva, J.M., Cabanas, A., Ballesteros, M., Hydrothermal pretreatment conditions to enhance ethanol production from poplar biomass (2003) Applied Biochemistry and Biotechnology - Part A Enzyme Engineering and Biotechnology, 108 (1-3), pp. 87-100. , DOI 10.1385/ABAB:105:1-3:87Zhao, Y., Lu, W.-J., Wang, H.-T., Li, D., Combined supercritical and subcritical process for cellulose hydrolysis to fermentable hexoses (2009) Environmental Science & Technology, 43, pp. 1565-1570Zhao, Y., Lu, W.-J., Wu, H.-Y., Liu, J.-W., Wang, H.-T., Optimization of supercritical phase and combined supercritical/ subcritical conversion of lignocellulose for hexose production by using a flow reaction system (2012) Bioresource TechnologyMochidzuki, K., Sakoda, A., Suzuki, M., Liquid-phase thermogravimetric measurement of reaction kinetics of the conversion of biomass wastes in pressurized hot water: A kinetic study (2003) Advances in Environmental Research, 7 (2), pp. 421-428. , DOI 10.1016/S1093-0191(02)00014-X, PII S109301910200014XZhao, Y., Lu, W.-J., Wang, H.-T., Yang, J.-L., Fermentable hexose production from corn stalks and wheat straw with combined supercritical and subcritical hydrothermal technology (2009) Bioresource Technology, 100, pp. 5884-5889Watchararuji, K., Goto, M., Sasaki, M., Shotipruk, A., Value-added subcritical water hydrolysate from rice bran and soybean meal (2008) Bioresource Technology, 99, pp. 6207-6213Mok, W.S.L., Antal Jr., M.J., Uncatalyzed solvolysis of whole biomass hemicellulose by hot compressed liquid water (1992) Industrial & Engineering Chemistry Research, 31, pp. 1157-1161Moreschi, S.R.M., Leal, J.C., Braga, M.E.M., Meireles, M.A.A., Ginger and turmeric starches hydrolysis using subcritical water + CO 2: The effect of the SFE pre-treatment (2006) Brazilian Journal of Chemical Engineering, 23 (2), pp. 235-242. , http://www.scielo.br/pdf/bjce/v23n2/29929.pdfKumar, S., Kothari, U., Kong, L., Lee, Y., Gupta, R.B., Hydrothermal pretreatment of switchgrass and corn stover for production of ethanol and carbon microspheres (2011) Biomass and Bioenergy, 35, pp. 956-968Prado, J.M., Dalmolin, I., Carareto, N.D.D., Basso, R.C., Meirelles, A.J.A., Vladimir Oliveira, J., Batista, E.A.C., Meireles, M.A.A., Supercritical fluid extraction of grape seed: Process scale-up, extract chemical composition and economic evaluation (2012) J. Food Engineering, 109, pp. 249-257Franca, L.F., Meireles, M.A.A., Extraction of oil from pressed palm oil (Elaes guineensis) fibers using supercritical CO2 (1997) Ciência e Tecnologia de Alimentos, 17, pp. 384-388Prado, J.M., Veggi, P.C., Meireles, M.A.A., Extraction methods for obtaining carotenoids from vegetables (2014) Current Analytical Chemistry, 10, pp. 29-66Sluiter, A., Hames, B., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D., Crocker, D., (2011) Determination of Structural Carbohydrates and Lignin in Biomass, p. 15. , NREL Golden, CO, USASluiter, A., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D., (2008) Determination of Extractives in Biomass, p. 9. , NREL Golden, CO, USASluiter, A., Hames, B., Hyman, D., Payne, C., Ruiz, R., Scarlata, C., Sluiter, J., Wolfe, J., (2008) Determination of Total Solids in Biomass and Total Dissolved Solids in Liquid Process Samples, p. 6. , NREL Golden, CO, USASluiter, A., Hames, B., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D., (2008) Determination of Ash in Biomass, p. 5. , NREL Golden, CO, USAHames, B., Scarlata, C., Sluiter, A., (2008) Determination of Protein Content in Biomass, p. 5. , NREL Golden, CO, USAPrado, J.M., Follegatti-Romero, L.A., Forster-Carneiro, T., Rostagno, M.A., Filho, F.M., Meireles, M.A.A., Hydrolysis of sugarcane bagasse in subcritical water (2014) J. Supercritical Fluids, 86, pp. 15-22Nelson, N., A photometric adaptation of the Somogyi method for the determination of glucose (1944) J. Biological Chemistry, 153, pp. 375-380Miller, G.L., Use of dinitrosalicylic acid reagent for determination of reducing sugar (1959) Analytical Chemistry, 31, pp. 426-428Rostagno, M.A., Manchón, N., D'Arrigo, M., Guillamón, E., Villares, A., García-Lafuente, A., Ramos, A., Martínez, J.A., Fast and simultaneous determination of phenolic compounds and caffeine in teas, mate, instant coffee, soft drink and energetic drink by high-performance liquid chromatography using a fused-core column (2011) Analytica Chimica Acta, 685, pp. 204-211Farías-Campomanes, A.M., Rostagno, M.A., Meireles, M.A.A., Production of polyphenol extracts from grape bagasse using supercritical fluids: Yield, extract composition and economic evaluation (2013) J. Supercritical Fluids, 77, pp. 70-78Ando, H., Sakaki, T., Kokusho, T., Shibata, M., Uemura, Y., Hatate, Y., Decomposition behavior of plant biomass in hot-compressed water (2000) Industrial & Engineering Chemistry Research, 39, pp. 3688-3693Lü, X., Saka, S., Hydrolysis of Japanese beech by batch and semi-flow water under subcritical temperatures and pressures (2010) Biomass and Bioenergy, 34, pp. 1089-1097Sakaki, T., Shibata, M., Sumi, T., Yasuda, S., Saccharification of cellulose using a hot-compressed water-flow reactor (2002) Industrial and Engineering Chemistry Research, 41 (4), pp. 661-665Sasaki, M., Kabyemela, B., Malaluan, R., Hirose, S., Takeda, N., Adschiri, T., Arai, K., Cellulose hydrolysis in subcritical and supercritical water (1998) J. Supercritical Fluids, 13, pp. 261-268Peterson, A.A., Vogel, F., Lachance, R.P., Fröling, M., Antal Jr., M.J., Tester, J.W., Thermochemical biofuel production in hydrothermal media: A review of sub-and supercritical water technologies (2008) Energy & Environmental Science, 1, pp. 32-65Pourali, O., Asghari, F.S., Yoshida, H., Production of phenolic compounds from rice bran biomass under subcritical water conditions (2010) Chemical Engineering J., 160, pp. 259-266Liu, C., Wyman, C.E., Impact of fluid velocity on hot water only pretreatment of corn stover in a flowthrough reactor (2004) Applied Biochemistry and Biotechnology - Part A Enzyme Engineering and Biotechnology, 115 (1-3), pp. 977-987Liu, C., Wyman, C.E., Partial flow of compressed-hot water through corn stover to enhance hemicellulose sugar recovery and enzymatic digestibility of cellulose (2005) Bioresource Technology, 96 (18 SPEC. ISS.), pp. 1978-1985. , DOI 10.1016/j.biortech.2005.01.012, PII S0960852405000659Sakaki, T., Shibata, M., Miki, T., Hirosue, H., Hayashi, N., Decomposition of cellulose in near-critical water and fermentability of the products (1996) Energy and Fuels, 10 (3), pp. 684-688Miyafuji, H., Nakata, T., Ehara, K., Saka, S., Fermentability of water-soluble portion to ethanol obtained by supercritical water treatment of lignocellulosics (2005) Applied Biochemistry and Biotechnology - Part A Enzyme Engineering and Biotechnology, 124 (1-3), pp. 963-971Nakata, T., Miyafuji, H., Saka, S., Bioethanol from cellulose with supercritical water treatment followed by enzymatic hydrolysis (2006) Applied Biochemistry and Biotechnology, 130 (1-3), pp. 476-485. , DOI 10.1385/ABAB:130:1:476Cantero, D.A., Dolores Bermejo, M., José Cocero, M., High glucose selectivity in pressurized water hydrolysis of cellulose using ultra-fast reactors (2013) Bioresource Technology, 135, pp. 697-703Schacht, C., Zetzl, C., Brunner, G., From plant materials to ethanol by means of supercritical fluid technology (2008) J. Supercritical Fluids, 46, pp. 299-321Sasaki, M., Adschiri, T., Arai, K., Kinetics of Cellulose Conversion at 25 MPa in Sub- and Supercritical Water (2004) AIChE Journal, 50 (1), pp. 192-202. , DOI 10.1002/aic.10018Zhu, G., Xiao, Z., Zhu, X., Yi, F., Wan, X., Reducing sugars production from sugarcane bagasse wastes by hydrolysis in sub-critical water (2013) Clean Technologies and Environmental Policy, 15, pp. 55-61Wiboonsirikul, J., Hata, S., Tsuno, T., Kimura, Y., Adachi, S., Production of functional substances from black rice bran by its treatment in subcritical water (2007) LWT - Food Science and Technology, 40 (10), pp. 1732-1740. , DOI 10.1016/j.lwt.2007.01.003, PII S0023643807000333Allen, S.G., Kam, L.C., Zemann, A.J., Antal Jr., M.J., Fractionation of sugar cane with hot, compressed, liquid water (1996) Industrial and Engineering Chemistry Research, 35 (8), pp. 2709-2715Öztürk, I., Irmak, S., Hesenov, A., Erbatur, O., Hydrolysis of kenaf (Hibiscus cannabinus L.) stems by catalytical thermal treatment in subcritical water (2010) Biomass and Bioenergy, 34, pp. 1578-1585Sasaki, M., Adschiri, T., Arai, K., Fractionation of sugarcane bagasse by hydrothermal treatment (2003) Bioresource Technology, 86 (3), pp. 301-304. , DOI 10.1016/S0960-8524(02)00173-6, PII S0960852402001736