Photo-mixotrophic Cultivation of Algae Euglena gracilis for Lipid Production

In the future, due to limited resources, a crisis of energy storing molecules (fuels), which are currently produced from crude mineral oil, is expected. One strategy to compensate a part of the oil deficiency is the production of biodiesel from microalgal lipids. As model microorganism for lipid production microalgae Euglena gracilis was selected and photo mixotrophic cultivation was performed in the stirred tank photobioreactor. During this research, medium composition and operational conditions of photo-bioreactor were optimized in order to define adequate cultivation conditions for algae biomass and lipid production. As low-cost and available complex carbon/ nitrogen source, corn steep liquor (CSL) was used to promote E. gracilis growth and lipid production. Due to the optimization of medium composition and cultivation conditions, lipid production was increased up to 29% of biomass dry weight in a two stage cultivation process inside one photo-bioreactor. Promising results obtained in this research encouraged us for further investigation

Application of Mixed Microbial Culture Biofilms for Manganese (II), Cobalt (II), and Chromium (VI) Biosorption by Horizontal Rotating Tubular Bioreactor

Industrial wastewater contaminated with toxic heavy metals is a big ecological and environmental problem. Applying biological materials to effectively remove and recover heavy metals from contaminated wastewaters has gained importance as promising alternative to conventional treatment techniques. Thus, the objective of the presented paper is the investigation of the capability of microorganisms, isolated from polluted (metal-laden) soil, to biosorb toxic metals from aqueous solutions. Biosorption process for heavy metal removal was conducted in a new pilot scale horizontal rotating tubular bioreactor (HRTB). This bioreactor provides conditions for microorganism’s growth in a form of suspended cells and biofilm. Biofilm is capable to protect microorganisms from interaction with toxic metals in the surrounding environment. Three metals were selected as model examples: cations of manganese and cobalt and hexavalent chromium (an oxyanion). Optimized bioreactor conditions, namely, medium inflow rate (F) and bioreactor rotation speed (n) for biofilm formation and metal removal were monitored, and under optimized bioreactor conditions, promising results were obtained

New Trends in the Ethanol Production as a Biofuel

Povećanje emisije stakleničkih plinova, energetska ovisnost i nestabilnost isporuke energenata posljedica su ubrzane potrošnje fosilnih goriva zbog ubrzanog rasta svjetske populacije i industrijalizacije. Bioetanol je postao atraktivno zamjensko biogorivo jer se proizvodi iz obnovljivih sirovina i ekološki je prihvatljiv. Upotrebljava se kao pogonsko gorivo i to kao hidrirani (96 %) ili bezvodni (u mješavinama s benzinom). Bioetanol se proizvodi fermentacijom s kvascem S. cerevisiae ili nekim drugim mikroorganizmom iz ugljikohidrata kao što su jednostavni šećeri, škrob i celuloza. Nakon fermentacije, bioetanol se izdvaja i pročišćava destilacijom i dehidracijom. Sastav je propisan specifikacijama za primjenu u motornim gorivima. Uobičajeni usjevi, kao što su kukuruz, šećerna repa i trska, zasad su osnovne sirovine za proizvodnju bioetanola. Međutim, proizvodnja bioetanola iz ovih sirovina ne može zadovoljiti globalne potrebe za bioetanolom, zbog njihove primarne uloge u prehrani ljudi i životinja. Lignoceluloza je pogodna sirovina za proizvodnju bioetanola jer je široko rasprostranjena, obnovljiva i ne upotrebljava se u prehrani. Proizvodnja bioetanola iz lignoceluloznih sirovina je složen proces, koji se u mnogim aspektima razlikuje od proizvodnje iz šećernih ili škrobnih sirovina. U ovom radu prikazane su dosadašnje i nove tehnologije u proizvodnji bioetanola uključujući primjenu različitih sirovina, postupaka proizvodnje i radnih mikroorganizama. Nadalje, navedene su mogućnosti integracije osnovnih koraka u bioprocesima proizvodnje s ciljem povećanja produktivnosti i smanjenja troškova proizvodnje.Rapidly growing fossil energy consumption, due to population and industrial growth, has caused increasing greenhouse-gas emissions, growing energy dependency and supply insecurity. Bioethanol has become an attractive alternative biofuel because of its environmental benefits and the fact that it is made from renewable resources. Ethanol is widely used as transport fuel, pure hydrous ethanol or anhydrous ethanol in mixtures with gasoline (Fig. 1). Bioethanol is produced from carbohydrates such as sugar, starch and cellulose by fermentation with yeast S. cerevisiae or other microorganisms. Thereupon, ethanol is separated and purifyed by distillation-rectification-dehydration to meet fuel specifications. Currently, conventional crops such as corn or sugarcane are the main feedstock for bioethanol production. Bioethanol production from the sucrose-containing feedstock is simpler compared to the starchy materials and the lignocellulosic biomass due to an additional step – feedstock hydrolysis. The process of ethanol production from starchy materials includes the hydrolysis of starch to glucose using α-amylase (1,4-α-D-glucan-4-glucanohydrolase) and glucoamylase (1,4-α-D-glucanglucohydrolase). Finally, the glucose is fermented to ethanol by yeast cells. Enzymatic hydrolysis of starch and fermentation of glucose can be carried out in different process configurations, such as separate hydrolysis and fermentation (SHF), and simultaneous saccharification and fermentation (SSF, Fig. 2). In consolidated bioprocessing (CBP), the conversion of starch into ethanol is performed in one step without added enzymes. This process configuration has potential to lower the cost of biomass processing due to elimination of operating and capital costs associated with dedicated enzyme production. Current bioethanol production from corn and sugarcane is unable to meet the global demand for bioethanol, due to their primary value as livestock feed and human food. The lignocellulosic biomass such as agricultural wastes (corn stover, crop straws, husks and bagasse), herbaceous crops (switchgrass), woody crops, forestry residue, waste paper and other wastes (municipal and industrial) is favourable feedstock for bioethanol production. The major advantages of lignocellulosic biomass are its renewable and ubiquitous nature and its noncompetitiveness with food crops. Ethanol production from lignocellulosic feedstock is complex and comprises two steps prior to fermentation: biomass pretreatment (breaking down the structure of the lignocellulosic matrix) and cellulose hydrolysis (enzymatic hydrolysis of cellulose to glucose). The lignocellulosic hydrolysate contains not only hexoses, but also pentoses that are not assimilated by yeast S. cerevisiae. Furthermore, the lignocellulosic hydrolysate contains a broad range of compounds that inhibit the yeast’s cells. The composition of the inhibitors depends on the type of the lignocellulosic material, and the chemistry and nature of the pretreatment process. The pretreated cellulose can be enzymatically hydrolysed either prior or simultaneously with glucose fermentation (Fig. 3). The four main steps involved in the process of lignocellulosic bioethanol production (pretreatment, cellulose hydrolysis, hexoses and pentoses fermentation) can be arranged in various process configurations, including separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SSCF) and consolidated bioprocessing (CBP, Fig. 3). Specific strains of bacteria and yeasts have been developed to ferment sugars released from lignocellulosic biomass and hydrolysed cellulose, through a selection of new strains and genetic engineering of traditional strains

Proizvodnja bioetanola iz kukuruznih oklasaka

Bioetanol je proizveden procesom istodobne saharifikacije i fermentacije (eng. Simultaneous saccharification and fermentation, SSF) s kvascem Saccharomyces cerevisiae na enzimskom hidrolizatu predobrađenih kukuruznih oklasaka. Istraživan je učinak trajanja predhidrolize kukuruznih oklasaka na učinkovitost procesa proizvodnje bioetanola te je uspoređen s konvencionalnim procesom SSF. Dvije smjese komercijalno dostupnih enzima rabljene su za hidrolizu sirovine; prva je sadržavala Celluclast 1.5L (Sigma) i β-glukozidazu (Carl Roth), a druga smjesa Celluclast 1.5L (Sigma) i Viscozyme L (Sigma). Dva dana predhidrolize imala su pozitivan učinak na prinos bioetanola, dok je dulje trajanje predhidrolize smanjilo prinos bioetanola. Najveća koncentracija etanola od 41,24 g dm−3 postignuta je u procesu SSF uz dva dana predhidrolize koja je iznosila 63,15 % teoretskog iskorištenja izračunatog na neobrađeni kukuruzni oklasak. Najveća ukupna produktivnost procesa od 0,36 g dm−3 h−1 postignuta je konvencionalnim SSF-om uz enzimsku smjesu koja je sadržavala Celluclast 1.5L (Sigma) i Viscozyme L (Sigma). Koncentracija etanola iznosila je 36,6 g dm−3, što je 56,02 % teoretskog prinosa etanola na neobrađeni kukuruzni oklasak

Photo-mixotrophic Cultivation of Algae Euglena gracilis for Lipid Production

In the future, due to limited resources, a crisis of energy storing molecules (fuels), which are currently produced from crude mineral oil, is expected. One strategy to compensate a part of the oil deficiency is the production of biodiesel from microalgal lipids. As model microorganism for lipid production microalgae Euglena gracilis was selected and photo mixotrophic cultivation was performed in the stirred tank photobioreactor. During this research, medium composition and operational conditions of photo-bioreactor were optimized in order to define adequate cultivation conditions for algae biomass and lipid production. As low-cost and available complex carbon/ nitrogen source, corn steep liquor (CSL) was used to promote E. gracilis growth and lipid production. Due to the optimization of medium composition and cultivation conditions, lipid production was increased up to 29% of biomass dry weight in a two stage cultivation process inside one photo-bioreactor. Promising results obtained in this research encouraged us for further investigation

Optimisation of algae Euglena gracilis cultivation conditions for vitamin A and vitamin E production

U ovom istraživanju proveden je uzgoj alge Euglena gracilis s ciljem proizvodnje vitamina A i vitamina E. U svrhu određivanja najpovoljnijih parametara za proizvodnju vitamina u bioreaktoru s mješalom provedena je optimizacija sastava hranjive podloge i uvjeta uzgoja E. gracilis, u Erlenmeyer tikvicama na laboratorijskoj tresilici. Tijekom uzgoja alge E. gracilis u bioreaktoru s mješalom primijenjen je dvostupanjski uzgoj. U prvom stupnju proveden je fotoheterotrofni uzgoj na Hutner-ovoj podlozi, a u drugom stupnju miksotrofni uzgoj na podlozi s ograničenim izvorom ugljika. Primjena dvostupanjskog procesa osigurala je relativno visoku produktivnost proizvodnje vitamina A (PrA = 0,07 mg/Lh) i vitamina E (PrE= 0,27 mg/Lh), a prinosi su iznosili vitamina A (YA = 6,53 mg/L) odnosno vitamina E (YE = 26,26 mg/L). Visoki prinosi vitamina E ukazuju na mogućnost primjene dvostupanjskog procesa njegove proizvodnje u industrijskom mjerilu.In this research, cultivation of algae Euglena gracilis was studied in order to produce vitamin A and vitamin E. The optimization of medium composition and cultivation conditions, in Erlenmeyer flasks on laboratory shaker, was done to define the most appropriate parameters for vitamin production in the stirred tank bioreactor. During cultivation of E. gracilis in the stirred tank bioreactor two-step process was examined. In the first step photoheterotrofic cultivation on the Hutner medium was done and in the second step photomixotrophically cultivation on the limited carbon source medium. In the two step process following bioprocess efficiency parameters were observed: productivity for vitamine A (PrA = 0.07 mg/Lh) and vitamin E (PrE= 0.27 mg/Lh) production as well as vitamin A (YA = 6.53 mg/L) and vitamin E (YE = 26.26 mg/L) yield. High vitamin E yield indicate potential of two-step processes for this vitamin industrial scale production

Microalgae – a potential source of lipids for biodiesel production

Biomasa mikroalgi predstavlja vrijednu sirovinu za proizvodnju farmaceutskih, prehrambenih i kozmetičkih proizvoda (proteina, masnih kiselina, vitamina, anti-oksidansa, pigmenata, lijekova i imunostimulansa), te proizvodnju biogoriva (biodizela). Temelj učinkovite proizvodnje biomase mikroalgi za dobivanje biogoriva primjena je bioprocesno inženjerskih znanja povezanih s izborom mikroalge, hranjive podloge, uvjeta i postupka vođenja bioprocesa u različitim bioreaktorskim sustavima, te metode izdvajanja i pročišćavanja biomase mikroalgi. Kriteriji izbora mikroalge određeni su fiziološkim potencijalom i mogućnošću mikroalge da uspješno nakuplja lipide tijekom bioprocesa. Izbor hranjive podloge, uvjeta i postupka vođenja bioprocesa ključni su za proizvodnju biomase mikroalgi s velikim udjelom lipida. Za dobivanje što veće količine biomase mikroalgi s ciljem proizvodnje biogoriva koriste se različiti bioreaktorski sustavi s jednom ili više podjedinica koji su opremljeni različitim sustavima za nadzor bioprocesa. Osim uvjeta i postupka vođenja bioprocesa u bioreaktoru za uspješnu proizvodnju biogoriva potrebno je izabrati i adekvatne metode za izdvajanje i pročišćavanje biomase odnosno lipida iz biomase mikroalgi. Stoga je u ovom radu dan i pregled metoda za izdvajanje i pročišćavanje biomase odnosno lipida iz biomase mikroalgi nakon uzgoja u bioreaktoru.Microalgal biomass represents valuable raw material for pharmaceuticals, food and cosmetic industry (proteins, fatty acids, vitamins, antioxidants, pigments, pharmaceuticals and immunostimulant) as well as for biofuels production (biodiesel). A base of efficient microalgal biomass production for biofuels production is the use of bioprocess engineering knowledge related to the selection of microalgae species, cultivation medium and conditions, bioprocess cultivation techniques in different bioreactor systems as well as microalgal biomass separation and purification. Selection criteria for microalgae species has to be related to the microalgae physiological potentials and its abilities to accumulate lipids during bioprocess. Cultivation medium and conditions as well as bioprocess cultivation techniques in bioreactor system are key parameters for successful production of microalgal biomass with high lipid content. In order to produce large quantities of microalgal biomass for biofuels production different bioreactor systems with one or more subunits (equipped with different monitoring systems) are used. Beside cultivation conditions and bioprocess cultivation techniques in bioreactor system for efficient biofuels production it is necessary to select appropriate methods for biomass as well as lipid separation and purification from microalgal biomass. Therefore, in this work the overview of different methods for biomass and lipids separation and purification from microalgal biomass is also presented

The Effect of Total Oxygen Concentraction in the Bottle on the Beer Quality During Storage

U ovom istraživanju provedeno je ispitivanje utjecaja ukupne koncentracije kisika u staklenoj boci na kakvoću piva donjeg vrenja tijekom skladištenja. Pivo je bilo skladišteno na temperaturi od 22 - 25°C u tamnoj prostoriji, a u pivu je bio prisutan kisik u tri različite ukupne početne koncentracije: 0,09 mg/L, 0,29 mg/L i 0,63 mg/L. Tijekom skladištenja (98 dana) u pivu je praćena promjena koncentracije trans-2-nonenala kao indikatora procesa oksidacije (starenja) piva, a dobiveni rezultati pokazuju da koncentracija trans-2-nonenala nije direktno ovisna o ukupnoj koncentraciji kisika u boci piva. U ovom istraživanju provedena je i senzorska analiza uzoraka piva koja je pokazala da povećane ukupne koncentracije kisika u boci izravno utječu na ocjenu kakvoće piva.In this research the effect of total packaging oxygen on the quality of bottled (glass bottle) lager beer during storage was studied. The beer was stored in a dark room at temperature of 22 - 25°C and it contained three different concentrations of total packaging oxygen: 0,09, 0,29 and 0,63 mg/L. During the 98 days storage period the concentration of trans-2-nonenal, a well known indicator of oxidation processes in the beer, was monitored. The results obtained in this research clearly show that the concentration of trans-2-nonenal is not directly related to the total oxygen concentration in the bottled beer. Sensory analysis of beer was also performed and obtained results clearly show that higher concentrations of total packaging oxygen directly effects beer quality and flavour