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  • 1.
    Akinbomi, Julius
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Wikandari, Rachman
    University of Borås, Faculty of Textiles, Engineering and Business.
    Taherzadeh, Mohammad J
    University of Borås, Faculty of Textiles, Engineering and Business.
    Enhanced Fermentative Hydrogen and Methane Production from an Inhibitory Fruit-Flavored Medium with Membrane-Encapsulated Cells.2015In: Membranes, ISSN 2077-0375, E-ISSN 2077-0375, Vol. 5, no 4Article in journal (Refereed)
    Abstract [en]

    This study focused on the possibility of improving fermentative hydrogen and methane production from an inhibitory fruit-flavored medium using polyvinylidene fluoride (PVDF) membrane-encapsulated cells. Hexanal, myrcene, and octanol, which are naturally produced in fruits such as apple, grape, mango, orange, strawberry, and plum, were investigated. Batch and semi-continuous fermentation processes at 55 °C were carried out. Presence of 5 g/L of myrcene, octanol, and hexanal resulted in no methane formation by fermenting bacteria, while encapsulated cells in the membranes resulted in successful fermentation with 182, 111, and 150 mL/g COD of methane, respectively. The flavor inhibitions were not serious on hydrogen-producing bacteria. With free cells in the presence of 5 g/L (final concentration) of hexanal-, myrcene-, and octanol-flavored media, average daily yields of 68, 133, and 88 mL/g COD of hydrogen, respectively, were obtained. However, cell encapsulation further improved these hydrogen yields to 189, 179, and 198 mL/g COD. The results from this study indicate that the yields of fermentative hydrogen and methane productions from an inhibitory medium could be improved using encapsulated cells.

  • 2.
    Wikandari, R.
    et al.
    University of Borås, School of Engineering.
    Millati, R.
    Cahyanto, M.N.
    Taherzadeh, M.J.
    University of Borås, School of Engineering.
    Biogas production from citrus waste by membrane bioreacto2014In: Membranes, ISSN 2077-0375, E-ISSN 2077-0375, Vol. 4, no 3, p. 596-607Article in journal (Refereed)
    Abstract [en]

    Rapid acidification and inhibition by d-limonene are major challenges of biogas production from citrus waste. As limonene is a hydrophobic chemical, this challenge was encountered using hydrophilic polyvinylidine difluoride (PVDF) membranes in a biogas reactor. The more sensitive methane-producing archaea were encapsulated in the membranes, while freely suspended digesting bacteria were present in the culture as well. In this membrane bioreactor (MBR), the free digesting bacteria digested the citrus wastes and produced soluble compounds, which could pass through the membrane and converted to biogas by the encapsulated cell. As a control experiment, similar digestions were carried out in bioreactors containing the identical amount of just free cells. The experiments were carried out in thermophilic conditions at 55 °C, and hydraulic retention time of 30 days. The organic loading rate (OLR) was started with 0.3 kg VS/m3/day and gradually increased to 3 kg VS/m3/day. The results show that at the highest OLR, MBR was successful to produce methane at 0.33 Nm3/kg VS, while the traditional free cell reactor reduced its methane production to 0.05 Nm3/kg VS. Approximately 73% of the theoretical methane yield was achieved using the membrane bioreactor.

  • 3.
    Wikandari, Rachma
    University of Borås, School of Engineering.
    Effect of fruit flavors on anaerobic digestion: inhibitions and solutions2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fruits are among the most important commodities in global trading due to its fundamental nutritional values. In 2012, the fruits supply was 115 kg/person/year, however, only 50 % of the fruits reached their consumers and the rest ended up as waste during the long fruit supply chain. The waste from fruits is mostly dumped or burned, creating a serious environmental problem. A more sustainable handling of the waste is therefore highly desirable. One of them is conversion of the fruits wastes into biogas through anaerobic digestion. One challenge with the conversion of fruits wastes into biogas is the presence of antimicrobial compounds in the fruits, which reduce the biogas yield or even cause a total failure of the process. Fruit flavors have been reported to have antimicrobial activity against several microorganisms and being responsible for the defense system in the fruits. However, there is only scarce information about the effect of fruit flavors on anaerobic digesting microbia. The objectives of the present thesis were: 1) to investigate the inhibitory activity of the fruit flavors on anaerobic digestion; 2) to remove the flavor compound by pretreatment; and 3) to protect the cell from the flavor compounds using a membrane bioreactor. The inhibitory activity of the fruit flavors was examined from different groups of flavors by adding a single flavor compound into the batch anaerobic digesting system, at three different concentrations. Among the flavors added, myrcene and octanol were found to exhibit a strong inhibitory activity, with 50 % reduction of the methane production at low concentrations, ca. 0.005–0.05 %. These flavors can be found in oranges, strawberries, grapes, plums, and mangoes. The other flavors tested showed moderate and low inhibitory activity, which might not affect the anaerobic digestion of the fruits wastes. In order to overcome the inhibitory effects of the fruit flavor, two approaches were proposed in this thesis, namely, fruit flavor removal by leaching pretreatment and cell protection from fruit flavor using a membrane bioreactor. Orange peel waste and D-limonene were used as a model of fruit waste and inhibitor, respectively. The leaching pretreatment uses solvent to extract the limonene from the orange peel. The methane yield increased by 356 % from 0.061 Nm3/kg VS to 0.217 Nm3/kg VS, by pretreating the peel using hexane with peel and a hexane ratio of 1:12 at room temperature for 10 min. Alternative to limonene removal, the cells were encased in a hydrophilic membrane, which is impermeable to hydrophobic limonene. This method yielded more than six times higher methane yield, compared to the free cell. At the highest organic loading rate, examined in this work, 3 g VS/L/day, the methane yield of the reactor containing the free cell was only 0.05 Nm3/kg VS, corresponding to 10 % of the theoretical yield, whereas 0.33 Nm3/kg VS methane yield was achieved using a membrane bioreactor corresponding to 75 % of the theoretical yield.

  • 4.
    Wikandari, Rachma
    et al.
    University of Borås, School of Engineering.
    Gudipudi, S.
    Pandiyan, I.
    Millati, R.
    Taherzadeh, M.J.
    University of Borås, School of Engineering.
    Inhibitory Effect of Fruit Flavors on Methane Production During Anaerobic Digestion2013In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 145, no IFIBiop, p. 188-192Article in journal (Refereed)
    Abstract [en]

    In order to improve biogas production from fruit wastes, the inhibitory effects of fruit flavors on anaerobic digestion were investigated. Batch anaerobic digestion was performed for 30 days using synthetic medium and thermophilic sludge. Three groups of flavor compounds i.e. aldehydes (hexanal, nonanal, and E-2-hexenal), terpenes (car-3-ene, α-pinene, and myrcene), and alcohol (octanol) at concentration of 0.005%, 0.05%, and 0.5% were examined. All the flavor compounds showed inhibitory effect on methane production. The highest methane reduction was obtained at addition of 0.5% of flavor compounds. For terpenoids, the presence of 0.5% of car-3-ene, myrcene, and α-pinene reduced 95%, 75%, and 77% of methane production, respectively. For aldehydes, addition of 0.5% concentration resulted in more than 99% methane reduction for hexanal and E-2-hexenal, and 84% methane reduction for nonanal. For alcohol, the presence of 0.5% octanol decreased 99% methane production.

  • 5.
    Wikandari, Rachma
    et al.
    University of Borås, School of Engineering.
    Gudipudi, S
    Pandiyan, I
    Yanti, H
    Millati, R
    Niklasson, C
    Taherzadeh, M.J.
    University of Borås, School of Engineering.
    Biogas production from fruit wastes: fruit flavors as booster or inhibitors?2012Conference paper (Refereed)
    Abstract [en]

    In order to improve biogas production from fruit waste, investigation of effect of fruit flavors on biogas production was carried out. The work was performed in batch anaerobic digestion using synthetic medium and thermophilic bacteria for 30 days. Twelve different flavors belonging to aldehydes (hexanal, nonanal, and E-2- hexenal), terpenes (carene, α-pinene, and myrcene), alcohol (octanol), lactone (furanone), and esters (methyl butyrate, ethyl butyrate, ethyl hexanoate, and hexyl acetate) were tested. Anaerobic digestion without addition of flavors was used as reference. For aldehyde groups, hexanal and nonanal showed inhibition effect at concentration of 0.005% whereas E-2-hexenal required higher concentration i.e. 0.05% to show its effect. Addition of 0.5% of hexanal, nonanal, and E-2-hexenal resulted in lower biogas production than that of the corresponding reference by factor of 276, 317 and 434%, respectively. Similar to aldehydes, all terpenes group showed inhibition at concentration of 0.005%. Addition of 0.5% of carene, α-pinene, and myrcene decreased biogas production by factor of 300, 255, and 330%, respectively compared to the reference. Moreover, in the presence of 0.5% of octanol and furanone reduced biogas production by factor of 433 and 183%, respectively compared to the reference. On the contrary, higher biogas production was obtained by addition of all esters tested. Methyl butyrate, ethyl butyrate, ethyl hexanoate, and hexyl acetate at concentration of 0.5% increased biogas production by factor of 291, 717, 542, and 640%, respectively compared to the reference. In conclusion, most of flavor compounds are inhibitor for biogas production for the exception of ester groups.

  • 6.
    Wikandari, Rachma
    et al.
    University of Borås, School of Engineering.
    Millati, R.
    Lennartsson, P.
    University of Borås, School of Engineering.
    Harmayani, E.
    Taherzadeh, M.J.
    University of Borås, School of Engineering.
    Isolation and Characterization of Zygomycetes Fungi from Tempe for Ethanol Production and Biomass Applications2012In: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291, Vol. 167, no 6, p. 1501-1512Article in journal (Refereed)
    Abstract [en]

    Mixed fungal cultures used for making tempe, a fermented soy bean food, were screened for biomass conversion. Thirty-two zygomycetes strains from two tempe cultures were isolated and identified as Rhizopus, Mucor, Rhizomucor, and Absidia species based upon morphology. The dry weight biomass of these strains contained 49% to 63% protein and 10-24% chitosan. The strains with the best growth performance were selected and registered at Culture Collection of Gothenburg University as Rhizomucor CCUG 61146 and Rhizomucor CCUG 61147. These strains were able to grow both aerobically and micro-aerobically. Their ethanol yields were 0.38-0.47, 0.19-0.22, and 0.31-0.38 g/g on glucose, xylose, and a mix sugars consisting of cellobiose, glucose, xylose, arabinose, galactose, and mannose, respectively. The biomass yield of the strains varied between 65 and 140 mg dry weight/g glucose.

  • 7.
    Wikandari, Rachma
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Nguyen, Huong
    Millati, Ria
    Niklasson, Claes
    Taherzadeh, Mohammad J
    University of Borås, Faculty of Textiles, Engineering and Business.
    Improvement of Biogas Production from Orange Peel Waste by Leaching of Limonene2015In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141Article in journal (Refereed)
    Abstract [en]

    Limonene is present in orange peel wastes and is known as an antimicrobial agent, which impedes biogas production when digesting the peels. In this work, pretreatment of the peels to remove limonene under mild condition was proposed by leaching of limonene using hexane as solvent. The pretreatments were carried out with homogenized or chopped orange peel at 20–40°C with orange peel waste and hexane ratio (w/v) ranging from 1 : 2 to 1 : 12 for 10 to 300 min. The pretreated peels were then digested in batch reactors for 33 days. The highest biogas production was achieved by treating chopped orange peel waste and hexane ratio of 12 : 1 at 20°C for 10 min corresponding to more than threefold increase of biogas production from 0.061 to 0.217 m3methane/kg VS. The solvent recovery was 90% using vacuum filtration and needs further separation using evaporation. The hexane residue in the peel had a negative impact on biogas production as shown by 28.6% reduction of methane and lower methane production of pretreated orange peel waste in semicontinuous digestion system compared to that of untreated peel.

  • 8.
    Wikandari, Rachma
    et al.
    University of Borås, School of Engineering.
    Youngsukkasem, S.
    University of Borås, School of Engineering.
    Millati, R.
    Taherzadeh, M.J.
    University of Borås, School of Engineering.
    Performance of semi-continuous membrane bioreactor in biogas production from toxic feedstock containing D-limonene2014In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 170, p. 350-355Article in journal (Refereed)
    Abstract [en]

    A novel membrane bioreactor configuration containing both free and encased cells in a single reactor was proposed in this work. The reactor consisted of 120 g/L of free cells and 120 g/L of encased cells in a polyvinylidene fluoride membrane. Microcrystalline cellulose (Avicel) and d-Limonene were used as the models of substrate and inhibitor for biogas production, respectively. Different concentrations of d-Limonene i.e., 1, 5, and 10 g/L were tested, and an experiment without the addition of d-Limonene was prepared as control. The digestion was performed in a semi-continuous thermophilic reactor for 75 days. The result showed that daily methane production in the reactor with the addition of 1 g/L d-Limonene was similar to that of control. A lag phase was observed in the presence of 5 g/L d-Limonene; however, after 10 days, the methane production increased and reached a similar production to that of the control after 15 days.

  • 9. Yanti, Heri
    et al.
    Wikandari, Rachma
    University of Borås, School of Engineering.
    Millati, Ria
    Niklasson, Claes
    Taherzadeh, Mohammad J.
    University of Borås, School of Engineering.
    Effect of ester compounds on biogas production: beneficial or detrimental?2014In: Energy Science & Engineering, Vol. 2, no 1, p. 22-30Article in journal (Refereed)
    Abstract [en]

    Esters are major flavor compounds in fruits, which are produced in high volume. The widespread availability of these compounds in nature attracts interest on their behavior in anaerobic digestion in waste and wastewater treatments. The aim of this work was to study the effects of various esters at different concentrations in anaerobic digestion followed by determination of their minimum inhibitory concentration (MIC), and to study the effect of chain length of functional group and alkyl chain of ester on methane production. Addition of methyl butanoate, ethyl butanoate, ethyl hexanoate, and hexyl acetate at concentration up to 5 g L−1 increased methane production, while their higher concentrations inhibited the digestion process. The MIC values for these esters were between 5 and 20 g L−1. Except hexyl acetate, the esters at concentration 5 g L−1 could act as sole carbon source during digestion. For ethyl esters, increasing number of carbon in functional group decreased methane production. For acetate esters, alkyl chain longer than butyl inhibited methane production. Effect of ester on methane production is concentration-dependent.

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