Martin R. Okos

Bio: Martin R. Okos is an academic researcher from Purdue University. The author has contributed to research in topics: Fermentation & Moisture. The author has an hindex of 33, co-authored 137 publications receiving 3407 citations. Previous affiliations of Martin R. Okos include University of Illinois at Urbana–Champaign & Ohio State University.

Comparative evaluation of ethanol production by xylose-fermenting yeasts presented high xylose concentrations

Abstract: Three strains ofPichiastipitis and three ofCandidashehatae were compared withPachysolentannophilus in their abilities to ferment xylose at concentrations as high as 200 g/L when subjected to both aerobic and microaerophilic conditions. Evaluations based on accumulated ethanol concentrations, ethanol productivities, xylose consumption, and ethanol and xylitol yields were determined from batch culture time courses. Of the strains considered,P.stipitis NRRL Y-7124 seemed most promising since it was able to utilize all but 7 g/L of 150 g/L xylose supplied aerobically to produce 52 g/L ethanol at a yield of 0.39 g per gram xylose (76% of theoretical yield) and at a rate comparable to the fastest shown byC.shehatae NRRL Y-12878. For all strains tested, fermentation results from aerobic cultures were more favorable than those from microaerophilic cultures.

Classification of drying models for porous solids

Abstract: Models to describe drying pmesses are necessary for engineering design and optimization. Many resenrch studies in the past century have had the objective of developing mathematical models to describe drying processes in porous solids. This review identifies key characteristics of drying models including controlling process resistances, internal mechanisms of moisture movement, and methods of model cufficient determination, model solution, and model validation. Similarities and differences between previous work are noted, and strategies for future drying model development are discussed.

Measurement and Prediction of Thermal Properties of Foods

Abstract: This report outlines thermal property measurement techniques and thermal property modelling of foods. The discussion on measurement technique focuses on thermal conductivity and thermal diffusivity only. Since thermal conductivity and thermal diffusivity measurements are based on the heat transfer mechanism, measurement apparatus is specifically designed for certain materials and environmental conditions. The probe technique designed for simultaneous measurement of thermal conductivity and thermal diffusivity has been one of the most widely used because it can be easily operated, and commercially produced. A PC-based probe apparatus is presented. Published models on thermal conductivity prediction are grouped according to their appropriate food system. It is proposed in this study that the thermal conductivity model of foods be made up of its components and a structural model that accounts for the component arrangement in the system. The Keey model was found the best structural model for porous foods while the parallel-perpendicular model worked well for frozen nonporous system. This model was also appropriate for meat measured along the fibers at above freezing temperatures. The rest of nonporous foods was found best predicted with the parallel model.

The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of biomass to methane: a review

Abstract: Among different conversion processes for biomass, biological anaerobic digestion is one of the most economic ways to produce biogas from various biomass substrates In addition to hydrolysis of polymeric substances, the activity and performance of the methanogenic bacteria is of paramount importance during methanogenesis The aim of this paper is primarily to review the recent literature about the occurrence of both acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of particulate biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing bacteria Both acetotrophic and hydrogenotrophic methanogens are essential for the last step of methanogenesis, but the reports about their roles during this phase of the process are very limited Despite, some conclusions can still be drawn At low concentrations of acetate, normally filamentous Methanosaeta species dominate, eg, often observed in sewage sludge Apparently, high concentrations of toxic ionic agents, like ammonia, hydrogen sulfide (H2S) and volatile fatty acids (VFA), inhibit preferably Methanosaetaceae and especially allow the growth of Methanosarcina species consisting of irregular cell clumps, eg, in cattle manure Thermophilic conditions can favour rod like or coccoid hydrogenotrophic methanogens Thermophilic Methanosarcina species were also observed, but not thermophilic Methanosaetae Other environmental factors could favour hydrogentrophic bacteria, eg, short or low retention times in a biomass reactor However, no general rules regarding process parameters could be derivated at the moment, which favours hydrogenotrophic methanogens Presumably, it depends only on the hydrogen concentration, which is generally not mentioned in the literature