SUMMARYProduction of biofuels from renewable feedstocks has captured considerable scientific attention since they could be used to supply energy and alternative fuels. Bioethanol is one of the most interesting biofuels due to its positive impact on the environment. Currently, it is mostly produced from sugar- and starch-containing raw materials. However, various available types of lignocellulosic biomass such as agricultural and forestry residues, and herbaceous energy crops could serve as feedstocks for the production of bioethanol, energy, heat and value-added chemicals. Lignocellulose is a complex mixture of carbohydrates that needs an efficient pretreatment to make accessible pathways to enzymes for the production of fermentable sugars, which after hydrolysis are fermented into ethanol. Despite technical and economic difficulties, renewable lignocellulosic raw materials represent low-cost feedstocks that do not compete with the food and feed chain, thereby stimulating the sustainability. Different bioprocess operational modes were developed for bioethanol production from renewable raw materials. Furthermore, alternative bioethanol separation and purification processes have also been intensively developed. This paper deals with recent trends in the bioethanol production as a fuel from different renewable raw materials as well as with its separation and purification processes.

SummaryBiodiesel and biogas are two very important sources of renewable energy worldwide, and particularly in EU countries. While biodiesel is almost exclusively used as transportation fuel, biogas is mostly used for production of electricity and heat. The application of more sophisticated purification techniques in production of pure biomethane from biogas allows its delivery to natural gas grid and its subsequent use as transportation fuel. While biogas is produced mostly from waste materials (landfills, manure, sludge from wastewater treatment, agricultural waste), biodiesel in EU is mostly produced from rapeseed or other oil crops that are used as food. This raises the 'food or fuel' concerns. To mitigate this problem considerable efforts have been done to use non-food feedstock for biodiesel production. These include all kinds of waste oils and fats, but recently more attention has been devoted to production of microbial oils by cultivation of microorganisms that are able to accumulate high amounts of lipids in their biomass. Promising candidates for microbial lipids production can be found www.ftb.com.hrPlease note that this is an unedited version of the manuscript that has been accepted for publication. This version will undergo copyediting and typesetting before its final form for publication. We are providing this version as a service to our readers. The published version will differ from this one as a result of linguistic and technical corrections and layout editing.2 among different strains of filamentous fungi, yeast, bacteria and microalgae. Feedstocks of interest are agricultural waste rich in carbohydrates as well as different lignocellulosic raw materials where some technical issues have to be resolved. In this work, recovery and purification of biodiesel and biogas were also considered.

Biodiesel is still mainly produced from different vegetable (e.g., rapeseed, palm, soybean, sunflower, and used cooking oils) oils and animal fats, and therefore it has a negative impact on food and feed prices. For biodiesel production as an alternative feedstock, lipids from oleaginous microorganisms could be used. One of the oleaginous microorganisms is yeast Trichosporon oleaginosus that has the capacity to grow and accumulate lipids on different lignocellulosic hydrolysates. In this study, corn cobs were pretreated by alkali at loading from 0.08 to 1.6 g/g dry weight of untreated (raw) corn cobs (g NaOH/gDW_UCC) at 121 °C for 30 min. In a further step, alkaline pretreated corn cobs were subjected to the enzymatic hydrolysis by using commercial multienzymes mixtures. The optimal alkali loading (0.16 g/gDW_UCC) was related to the highest glucose and xylose yields which were observed during enzymatic hydrolysis of substrate. In this study, T. oleaginosus was applied for lipid production on the enzymatic corn cobs hydrolysates by following bioprocess configurations: separate hydrolysis and lipid production (SHLP) and simultaneous saccharification and lipid production (SSLP). The SSLP was characterized by higher lipid yield (88.88 mg/gDW_UCC) and productivity (2.4 g/(L day)) as well as significant bioprocess time reduction. On the basis of the above-mentioned facts, it is obvious that SSLP with T. oleaginosus has great potential for application in industrial scale.

Fossil fuels are still major energy sources, but the search for renewable energy sources has been encouraged. Bioethanol has been recognized as an alternative to fossil fuels and nowadays it represents more than 90% of the global biofuel production. Bioethanol production from raw sugar beet cossettes as a semi-solid substrate was studied. The study was carried out in the horizontal rotating tubular bioreactor (HRTB) with Saccharomyces cerevisiae as a microbial production strain. The impact of different combinations of HRTB operational parameters such as, rotation speed (5-15 min), rotation type [constant or interval (3-15 min h)] and working volume (ratio V /V = 0.2-0.7) on the bioethanol production was examined. In this study, the highest bioprocess efficiency parameters ([Formula: see text] = 0.47 g g, E = 87.36% and Pr = 0.618 g L h) were observed at 0.20 V /V, interval rotation of 12 min h and rotation speed of 15 min. It has to be pointed out that bioethanol production efficiency in the HRTB was on the similar level as observed by bioethanol production from the raw sugar beet juice. Naturally present microorganisms of sugar beet could have a significant impact on bioethanol production. Higher yeast inoculation rate could reduce contaminant activities and, consequently, the bioethanol production efficiency would be improved.

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