Impact of Furfural on Rapid Ethanol Production Using a Membrane Bioreactor

A membrane bioreactor was developed to counteract the inhibition effect of furfural in ethanol production. Furfural, a major inhibitor in lignocellulosic hydrolyzates, is a highly toxic substance which is formed from pentose sugars released during the acidic degradation of lignocellulosic materials. Continuous cultivations with complete cell retention were performed at a high dilution rate of 0.5 h−1. Furfural was added directly into the bioreactor by pulse injection or by addition into the feed medium to obtain furfural concentrations ranging from 0.1 to 21.8 g L−1. At all pulse injections of furfural, the yeast was able to convert the furfural very rapidly by in situ detoxification. When injecting 21.8 g L−1 furfural to the cultivation, the yeast converted it by a specific conversion rate of 0.35 g g−1 h−1. At high cell density, Saccharomyces cerevisiae could tolerate very high furfural levels without major changes in the ethanol production. During the continuous cultures when up to 17.0 g L−1 furfural was added to the inlet medium, the yeast successfully produced ethanol, whereas an increase of furfural to 18.6 and 20.6 g L−1 resulted in a rapidly decreasing ethanol production and accumulation of sugars in the permeate. This study show that continuous ethanol fermentations by total cell retention in a membrane bioreactor has a high furfural tolerance and can conduct rapid in situ detoxification of medium containing high furfural concentrations

Concepts for improving ethanol productivity from lignocellulosic materials : encapsulated yeast and membrane bioreactors

Lignocellulosic biomass is a potential feedstock for production of sugars, which can be fermented into ethanol. The work presented in this thesis proposes some solutions to overcome problems with suboptimal process performance due to elevated cultivation temperatures and inhibitors present during ethanol production from lignocellulosic materials. In particular, continuous processes operated at high dilution rates with high sugar utilisation are attractive for ethanol fermentation, as this can result in higher ethanol productivity. Both encapsulation and membrane bioreactors were studied and developed to achieve rapid fermentation at high yeast cell density. My studies showed that encapsulated yeast is more thermotolerant than suspended yeast. The encapsulated yeast could successfully ferment all glucose during five consecutive batches, 12 h each at 42 °C. In contrast, freely suspended yeast was inactivated already in the second or third batch. One problem with encapsulation is, however, the mechanical robustness of the capsule membrane. If the capsules are exposed to e.g. high shear forces, the capsule membrane may break. Therefore, a method was developed to produce more robust capsules by treating alginate-chitosan-alginate (ACA) capsules with 3-aminopropyltriethoxysilane (APTES) to get polysiloxane-ACA capsules. Of the ACA-capsules treated with 1.5% APTES, only 0–2% of the capsules broke, while 25% of the untreated capsules ruptured within 6 h in a shear test. In this thesis membrane bioreactors (MBR), using either a cross-flow or a submerged membrane, could successfully be applied to retain the yeast inside the reactor. The cross-flow membrane was operated at a dilution rate of 0.5 h-1 whereas the submerged membrane was tested at several dilution rates, from 0.2 up to 0.8 h-1. Cultivations at high cell densities demonstrated an efficient in situ detoxification of very high furfural levels of up to 17 g L-1 in the feed medium when using a MBR. The maximum yeast density achieved in the MBR was more than 200 g L-1. Additionally, ethanol fermentation of nondetoxified spruce hydrolysate was possible at a high feeding rate of 0.8 h-1 by applying a submerged membrane bioreactor, resulting in ethanol productivities of up to 8 g L-1 h-1. In conclusion, this study suggests methods for rapid continuous ethanol production even at stressful elevated cultivation temperatures or inhibitory conditions by using encapsulation or membrane bioreactors and high cell density cultivations.Akademisk avhandling som för avläggande av teknologie doktorsexamen vid Chalmers tekniska högskola försvaras vid offentlig disputation den 4 april 2014, klockan 9:30 i KE-salen, Kemigården 4, Göteborg.</p

Production of ethanol and biomass from orange peel waste by Mucor indicus

For the citrus processing industry the disposal of fresh peels has become a major concern for manyfactories. Orange peels are the major solid by-product. Dried orange peels have a high content ofpectin, cellulose and hemicellulose, which make it suitable as fermentation substrate when hydrolyzed.The present work aims at utilizing orange peels for the production of ethanol by using the fungusMucor indicus. Hence, producing a valuable product from the orange peel waste. The biomass growthwas also examined, since the biomass of the fungus can be processed into chitosan, which also is avaluable material.The work was first focused on examining the fungus ability to assimilate galacturonic acid and severalother sugars present in orange peel hydrolyzate (fructose, glucose, galactose, arabionose, and xylose).Fructose and glucose are the sugars which are consumed the fastest whereas arabinose, xylose andgalacturonic acid are assimilated much slower.One problem when using orange peels as raw material is its content of peel oils (mainly D-limonene),which has an immense antimicrobial effect on many microorganism even at low concentrations. Inorder to study M. indicus sensitivity to peel oil the fungus was grown in medium containing differentconcentrations of D-limonene.At very low limonene concentrations the fungal growth was delayed only modestly, hence a couple ofhours when starting from spores and almost nothing when starting with biomass. Increasing theconcentration to 0.25% (v/v) and above halted the growth to a large extent. However, the fungus wasable to grow even at a limonene concentration of 1.0%, although, at very reduced rate. Cultivationsstarted from spore-solution were more sensitive than those started with biomass.Orange peels were hydrolyzed by two different methods to fermentable sugars, namely by dilute acidhydrolysis (0.5% (v/v) H2SO4) at 150 °C and by enzymatic hydrolysis by cellulase, pectinase and β-glucosidase. The fungus was able to produce ethanol with a maximum yield of about 0.36 g/g after 24h when grown on acid hydrolyzed orange peels both by aerobic and anaerobic cultivation. Apreliminary aerobic cultivation on enzymatic hydrolyzed orange peels gave a maximum ethanol yieldof 0.33 g/g after 26 h.The major metabolite produced during the cultivations was ethanol. Apart from ethanol, glycerol wasthe only component produced in significant amounts. In cultivations performed aerobically on acidandenzymatic hydrolyzed orange peels the glycerol yields were 0.048 g/g after 24 h.Two different techniques were also examined in order to evaluate if the methods could be use asbiomass determining methods when solid particles are present in the culture medium. The problemwith solid particles is that they will be buried inside the fungal biomass matrix. Hence makingseparation impossible prior to dry weight determination in the ordinary way. However, none of themethods involving chitin extraction or chitosan extraction did show any good results.The results from the present work are rather clear, M. indicus was able to grow and produce bothethanol and biomass even when limonene was present in the culture medium. The maximum ethanolyield was achieved after about 24 h in cultivations performed on both acid hydrolyzed and enzymatichydrolyzed orange peels. However, in order to say if the method can be applicable at industrial scaleand made economically feasible the subject has to be investigated further

Production of ethanol and biomass from orange peel waste by Mucor indicus

For the citrus processing industry the disposal of fresh peels has become a major concern for manyfactories. Orange peels are the major solid by-product. Dried orange peels have a high content ofpectin, cellulose and hemicellulose, which make it suitable as fermentation substrate when hydrolyzed.The present work aims at utilizing orange peels for the production of ethanol by using the fungusMucor indicus. Hence, producing a valuable product from the orange peel waste. The biomass growthwas also examined, since the biomass of the fungus can be processed into chitosan, which also is avaluable material.The work was first focused on examining the fungus ability to assimilate galacturonic acid and severalother sugars present in orange peel hydrolyzate (fructose, glucose, galactose, arabionose, and xylose).Fructose and glucose are the sugars which are consumed the fastest whereas arabinose, xylose andgalacturonic acid are assimilated much slower.One problem when using orange peels as raw material is its content of peel oils (mainly D-limonene),which has an immense antimicrobial effect on many microorganism even at low concentrations. Inorder to study M. indicus sensitivity to peel oil the fungus was grown in medium containing differentconcentrations of D-limonene.At very low limonene concentrations the fungal growth was delayed only modestly, hence a couple ofhours when starting from spores and almost nothing when starting with biomass. Increasing theconcentration to 0.25% (v/v) and above halted the growth to a large extent. However, the fungus wasable to grow even at a limonene concentration of 1.0%, although, at very reduced rate. Cultivationsstarted from spore-solution were more sensitive than those started with biomass.Orange peels were hydrolyzed by two different methods to fermentable sugars, namely by dilute acidhydrolysis (0.5% (v/v) H2SO4) at 150 °C and by enzymatic hydrolysis by cellulase, pectinase and β-glucosidase. The fungus was able to produce ethanol with a maximum yield of about 0.36 g/g after 24h when grown on acid hydrolyzed orange peels both by aerobic and anaerobic cultivation. Apreliminary aerobic cultivation on enzymatic hydrolyzed orange peels gave a maximum ethanol yieldof 0.33 g/g after 26 h.The major metabolite produced during the cultivations was ethanol. Apart from ethanol, glycerol wasthe only component produced in significant amounts. In cultivations performed aerobically on acidandenzymatic hydrolyzed orange peels the glycerol yields were 0.048 g/g after 24 h.Two different techniques were also examined in order to evaluate if the methods could be use asbiomass determining methods when solid particles are present in the culture medium. The problemwith solid particles is that they will be buried inside the fungal biomass matrix. Hence makingseparation impossible prior to dry weight determination in the ordinary way. However, none of themethods involving chitin extraction or chitosan extraction did show any good results.The results from the present work are rather clear, M. indicus was able to grow and produce bothethanol and biomass even when limonene was present in the culture medium. The maximum ethanolyield was achieved after about 24 h in cultivations performed on both acid hydrolyzed and enzymatichydrolyzed orange peels. However, in order to say if the method can be applicable at industrial scaleand made economically feasible the subject has to be investigated further

Fast co-pyrolysis of wood and plastic : Evaluation of the primary gaseous products

Bio-oil derived from fast pyrolysis of wood contains oxygenates and has a relatively low heating value. These are challenges that need to be tackled if wood-derived bio-oil is to be used as drop-in fuels. The bio-oil can be obtained by condensation of gaseous products. Using a material with no oxygen in addition to wood during fast pyrolysis could be a technique to reduce the formation of oxygenates and promote a hydrocarbon-rich product. This work aims to evaluate the primary gaseous products formed during fast co-pyrolysis of birch wood and plastic. The pyrolysis was performed in a micropyrolyser at 600 °C with a residence time of 5 s. Birch wood and plastic were melt-mixed at different weight ratios to study possible interaction effects upon pyrolysis. The different plastics used were low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS). The total gaseous product was between 10–20 wt% from Wood-LDPE or Wood-PP, while it was in the range 15–90 wt% from Wood-PS. The analysis of gas product found that the formation of oxygenates (up to 9 wt%) was lower than expected (up to 14 wt%) for the mixtures of wood and plastic compared to the pure materials (about 18 wt%). The reduction of oxygenates (up to 90 %) was mainly due to a lower production of ketones, carboxylic acids and aldehydes. Maximum hydrocarbons in the gas phase from binary mixtures were around 8, 15 and 55 wt% from Wood-LDPE, Wood-PP and Wood-PS, respectively. The most significant difference between experimental and estimated values assuming no interaction among hydrocarbons was observed in the case of alkenes and alkanes for Wood-LDPE, as well as alkanes for Wood-PS, while the Wood and PP mixture showed almost no signs of interaction. This work is beneficial for understanding interactions between wood and plastics, and could be used to reduce the amount of oxygenates from wood pyrolysis and reduce the need for upgrading

Gaseous products from primary reactions of fast plastic pyrolysis

This study aimed to establish primary reactions and identify gaseous products during fast pyrolysis of low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS). Fast pyrolysis was performed by using Py-GC/MS/FID at 574 ± 22 °C for 5 s. Gaseous fractions formed during pyrolysis of LDPE, PP and PS were 14 ± 1 wt%, 31 ± 3 wt% and 103 ± 12 wt%, respectively. The main gaseous compounds from LDPE were butane, 1-pentane and 1-hexene. PP pyrolysis gave propene, pentane and 2,4-dimethyl-1-heptene as the main gaseous compounds. Styrene monomer was the dominant gas from PS. The results showed that polyolefin (PP and PE) produced aliphatic hydrocarbons, while PS formed aromatic hydrocarbons. Furthermore, the proposed mechanism suggests that both inter- and intra-molecular hydrogen transfer occur during PP and PE pyrolysis. PS pyrolysis involves a C-C cleavage at the aliphatic side chain. This work is important to understand the mechanism of gas formation of primary reactions from pyrolysis of common plastics

Primary Products from Fast Co-Pyrolysis of Palm Kernel Shell and Sawdust

Co-pyrolysis is one possible method to handle different biomass leftovers. The success of the implementation depends on several factors, of which the quality of the produced bio-oil is of the highest importance, together with the throughput and constraints of the feedstock. In this study, the fast co-pyrolysis of palm kernel shell (PKS) and woody biomass was conducted in a micro-pyrolyser connected to a Gas Chromatograph–Mass Spectrometer/Flame Ionisation Detector (GC–MS/FID) at 600 °C and 5 s. Different blend ratios were studied to reveal interactions on the primary products formed from the co-pyrolysis, specifically PKS and two woody biomasses. A comparison of the experimental and predicted yields showed that the co-pyrolysis of the binary blends in equal proportions, PKS with mahogany (MAH) or iroko (IRO) sawdust, resulted in a decrease in the relative yield of the phenols by 19%, while HAA was promoted by 43% for the PKS:IRO-1:1 pyrolysis blend, and the saccharides were strongly inhibited for the PKS:MAH-1:1 pyrolysis blend. However, no difference was observed in the yields for the different groups of compounds when the two woody biomasses (MAH:IRO-1:1) were co-pyrolysed. In contrast to the binary blend, the pyrolysis of the ternary blends showed that the yield of the saccharides was promoted to a large extent, while the acids were inhibited for the PKS:MAH:IRO-1:1:1 pyrolysis blend. However, the relative yield of the saccharides was inhibited to a large extent for the PKS:MAH:IRO-1:2:2 pyrolysis blend, while no major difference was observed in the yields across the different groups of compounds when PKS and the woody biomass were blended in equal amounts and pyrolysed (PKS:MAH:IRO-2:1:1). This study showed evidence of a synergistic interaction when co-pyrolysing different biomasses. It also shows that it is possible to enhance the production of a valuable group of compounds with the right biomass composition and blend ratio.

Primary Products from Fast Co-Pyrolysis of Palm Kernel Shell and Sawdust

Co-pyrolysis is one possible method to handle different biomass leftovers. The success of the implementation depends on several factors, of which the quality of the produced bio-oil is of the highest importance, together with the throughput and constraints of the feedstock. In this study, the fast co-pyrolysis of palm kernel shell (PKS) and woody biomass was conducted in a micro-pyrolyser connected to a Gas Chromatograph–Mass Spectrometer/Flame Ionisation Detector (GC–MS/FID) at 600 °C and 5 s. Different blend ratios were studied to reveal interactions on the primary products formed from the co-pyrolysis, specifically PKS and two woody biomasses. A comparison of the experimental and predicted yields showed that the co-pyrolysis of the binary blends in equal proportions, PKS with mahogany (MAH) or iroko (IRO) sawdust, resulted in a decrease in the relative yield of the phenols by 19%, while HAA was promoted by 43% for the PKS:IRO-1:1 pyrolysis blend, and the saccharides were strongly inhibited for the PKS:MAH-1:1 pyrolysis blend. However, no difference was observed in the yields for the different groups of compounds when the two woody biomasses (MAH:IRO-1:1) were co-pyrolysed. In contrast to the binary blend, the pyrolysis of the ternary blends showed that the yield of the saccharides was promoted to a large extent, while the acids were inhibited for the PKS:MAH:IRO-1:1:1 pyrolysis blend. However, the relative yield of the saccharides was inhibited to a large extent for the PKS:MAH:IRO-1:2:2 pyrolysis blend, while no major difference was observed in the yields across the different groups of compounds when PKS and the woody biomass were blended in equal amounts and pyrolysed (PKS:MAH:IRO-2:1:1). This study showed evidence of a synergistic interaction when co-pyrolysing different biomasses. It also shows that it is possible to enhance the production of a valuable group of compounds with the right biomass composition and blend ratio.

Ethanol production at elevated temperatures using encapsulation of yeast

The ability of macroencapsulated Saccharomyces cerevisiae CBS 8066 to produce ethanol at elevated temperatures was investigated in consecutive batch and continuous cultures. Prior to cultivation yeast was confined inside alginate-chitosan capsules composed of an outer semi-permeable membrane and an inner liquid core. The encapsulated yeast could successfully ferment 30 g/L glucose and produce ethanol at a high yield in five consecutive batches of 12 h duration at 42 degrees C, while freely suspended yeast was completely inactive already in the third batch. A high ethanol production was observed also through the first 48 h at 40 degrees C during continuous cultivation at D = 0.2 h(-1) when using encapsulated cells. The ethanol production slowly decreased in the following days at 40 degrees C. The ethanol production was also measured in a continuous cultivation in which the temperature was periodically increased to 42-45 degrees C and lowered to 37 degrees C again in periods of 12 h. Our investigation shows that a non-thermotolerant yeast strain improved its heat tolerance upon encapsulation, and could produce ethanol at temperatures as high as 45 degrees C for a short time. The possibility of performing fermentations at higher temperatures would greatly improve the enzymatic hydrolysis in simultaneous saccharification and fermentation (SSF) processes and thereby make the bioethanol production process more economically feasible

Oxalylhydrazide and Malonohydrazide as building block for the synthesis of new substituted Pyrazoles with antioxidant activities

Four series of pyrazole derivatives (2a-j), (3a-j), (4a-j), (6a-j) and (7a-j) were synthesized. The first series of pyrazole derivatives (2a-j) were synthesized by the cyclocondensation reaction of oxalyldihydrazide 1 with various numbers of ß-diketones in molecular ratio 1:2 respectively. The second and third series of pyrazole derivatives (3aj) and (4a-j) were synthesized via cyclocondensation reaction of corresponding pyrazole derivative (2a-j) with thiourea and urea. While the series of pyrazoles (6a-j) were synthesized via cyclocondensation reaction of malonodihydrazide 5 with the same ß-diketones under identical molecular ratio (1:2). The series of tripyrazoles compounds (7a-j) were synthesized by cyclocondensation reaction of the hydrazine hydrate with corresponding pyrazole derivatives (6a-j) in molecular ratio 1:1. Compounds (6h), (2h) and (7h) showed higher antioxidant activity at 10µg/ml concentration compared to standard anti-oxidant. On the other hand compounds (6h), (6g) and (2h) at 40µg/ml concentration showed maximum anti-lipid peroxidation comparable to vitamin E. Structure of newly synthesized compounds were confirmed by elemental analysis and spectral IR, 1HNMR, 13CNMR data. The title compounds represent a novel class of antioxidant agents