Ethanol production using Paenibacillus strain J2 was studied on carbohydrates and lignocellulosic biomass hydrolysates including grass (Phleum pratense) and barley straw (Hordeum vulgare). The strain has a broad substrate spectrum; fermentation of glucose yielded ethanol (major product), acetate, butyrate (minor), hydrogen, and carbon dioxide. At glucose concentrations below 30 mM fermentation was not inhibited. Higher substrate loadings resulted in decreased glucose utilization and a shift of end products towards butyrate. The maximum yields of ethanol were 1.45 mol ethanol mol glucose -1 . The end products from lignocellulosic (4.5 g L -1 dw) biomass hydrolysates pretreated with 0.5% HCl or NaOH (control was unpretreated) prior to cellulase treatment were investigated. Ethanol production from cellulose hydrolysates without chemical pre-treatment yielded 5.5 mM ethanol g -1 with lower yields from paper and lignocellulosic biomasses (1.2-1.7 mM g -1 ). Ethanol production was enhanced by dilute acid or base pre-treatment combined with enzymatic treatment with the highest yields from grass (3.2 mM ethanol g -1 ).Key words: Bioethanol, Lignocellulosic biomass, Paenibacillus, Thermophiles YFIRLIT Etanól framleiðsla hjá Paenibacillus, stofni J2 var rannsakaður á sykrum og hýdrólýstötum úr flóknum lífmassa, m.a. vallarfoxgrasi (Phleum pratense) og hveitihálmi (Hordeum vulgare). Stofninn var með breytt hvarfefnasvið; gerjun á glúkósa leiddi til myndunar á etanóli (meginafurð), ediksýru, smjörsýru, vetnis og koltvísýrings. Of hár upphafsstyrkur (> 30 mM) glúkósa leiddi til hindrunar á niðurbroti hans og aukinnar framleiðslu á smjörsýru. Hámarksframleiðsla á etanóli var 1.45 mól etanól mól glúkósa -1 . Lokaafurðir úr hýdrólýsötum úr flóknum lífmassa (4.5 g L -1 þurrvigt) sem var formeðhöndlaður með annað hvort 0.5% HCl eða NaOH auk sellulasa meðhöndlunar var rannsökuð. Etanól framleiðsla úr sellulósa án efnafraeðilegrar formeðhöndlunar gaf af sér 5.5 mM etanól g -1 en minni nýting var á pappír og flóknum lífmassa (1.2-1.7 mM g -1 ). Etanólframleiðsla á grasi jókst með sýru-og basameðhöndlun ásamt ensímformeðhöndlun, en hámarksnýting var 3.2 mM etanól g -1 .www.ias.is http://dx