Daniela Cuna - Academia.edu (original) (raw)

Papers by Daniela Cuna

Research paper thumbnail of Biorefineries

Research paper thumbnail of Electrophoretic Deposition of Lignin Reinforced Polymer Coatings

Key Engineering Materials, Jul 1, 2015

Composite coatings based on PEEK and Lignin were obtained by EPD. The addition of Lignin had some... more Composite coatings based on PEEK and Lignin were obtained by EPD. The addition of Lignin had some beneficial effects, the most relevant being an increased coating adhesion on conductive substrates. Before using in EPD suspensions, Lignin was functionalised by a carbonyl group. This functionalisation produced chemical interactions between PEEK powder and Lignin, and, as a consequence, better results in terms of both EPD efficiency and adhesion coating. Moreover, the addition of Lignin increased the hydrophobicity of PEEK coatings when they were thermally treated at temperature lower than the melting point of PEEK.

Research paper thumbnail of Bioethanol production from steam-pretreated corn stover through an isomerase mediated process

New Biotechnology, Mar 1, 2014

Agricultural by-products such as corn stover are considered strategic raw materials for the produ... more Agricultural by-products such as corn stover are considered strategic raw materials for the production of second-generation bioethanol from renewable and non-food sources. This paper describes the conversion of steam-pretreated corn stover to ethanol utilising a multi-step process including enzymatic hydrolysis, isomerisation, and fermentation of mixed hydrolysates with native Saccharomyces cerevisiae. An immobilised isomerase enzyme was used for the xylose isomerisation along with high concentrations of S. cerevisiae. The objective was to assess the extent of simultaneity of the various conversion steps, through a detailed analysis of process time courses, and to test this process scheme for the conversion of lignocellulosic hydrolysates containing several inhibitors of the isomerase enzyme (e.g. metal ions, xylitol and glycerol). The process was tested on two types of hydrolysate after acid-catalysed steam pretreatment: (a) the water soluble fraction (WSF) in which xylose was the largest carbon source and (b) the entire slurry, containing both cellulose and hemicellulose carbohydrates, in which glucose predominated. The results indicated that the ethanol concentration rose when the inoculum concentration was increased in the range 10-75 g/L. However, when xylose was the largest carbon source, the metabolic yields were higher than 0.51 g ethanol /g consumed sugars probably due to the use of yeast internal cellular resources. This phenomenon was not observed in the fermentation of mixed hydrolysates obtained from the entire pretreated product and in which glucose was the largest carbon source. The ethanol yield from biomass suspensions with dry matter (DM) concentrations of 11-12% (w/v) was 70% based on total sugars (glucose, xylose, galactose). The results suggest that xylulose uptake was more effective in mixed hydrolysates containing glucose levels similar to, or higher than, xylose. Analysis of the factors that limit isomerase activity in lignocellulosic hydrolysates excluded any inhibition due to residual calcium ions after the detoxification of the hemicellulose hydrolysates with Ca(OH) 2. By contrast, most of the enzyme activity ceased during the fermentation of the entire slurry after steam explosion, probably due to synergistic inhibition effects of various fermentation coproducts.

Research paper thumbnail of Chlorinated hydrocarbons and heavy metals in tissues of Striped dolphin (Stenella coeruleoalba) stranded along the Apulian and Sicilian coasts (Summer 1991)

Research paper thumbnail of Alternative exploitation of Cynara spp. biodiversity in a bioeconomy context

Research paper thumbnail of Effect of treatments on the aging behaviour of hemp fibres for building construction in the Mediterranean Area

Journal of Building Engineering, 2017

The aim of this work is to study the influence of selected treatments on the behaviour of hemp fi... more The aim of this work is to study the influence of selected treatments on the behaviour of hemp fibres when used as insulation material in building envelopes, with particular regard to construction in the Mediterranean Area. In particular, the effects of treatments with salicylic acid and a natural monoterpenes phenol, for enhancing the resistance to degradation of hemp fibres to microbial attacks, were evaluated. Several types of hemp mats were prepared and contaminated with two fungal microorganisms and then subjected to accelerated weathering cycles in a climatic chamber, together with a hollow brick whose some holes were filled with chemically treated and untreated fibres. The experiment pointed out that, within the duration of the two-months long accelerated weathering test, simulating one year of service life in Mediterranean Area, neither fungal contamination nor significant changes in mass, colour and visual appearance, as well as structural properties and morphology, were observed for both the treated and untreated fibres. Nevertheless, the trend of temperatures and relative humidity realized inside the filled holes of the hollow brick underlined that the treated fibres showed a lower capacity to adsorb and desorb moisture with respect to untreated fibres. This behaviour is considered favourable, because it reduces the risk of moisture retention giving, in principle, advantages in terms of deterioration and resistance of the fibres to fungal attack. The differences of behaviour between treated and untreated hemp mats were investigated through XRD and FTIR analysis which revealed that the former had higher crystallinity and therefore lower capacity to uptake water. Highlights  accelerated weathering test on Mediterranean Area;  hemp fibres as insulating materials in Mediterranean Area;  Influence of treatments with natural substances on hygro-thermal behaviour of hemp fibres;  Evaluation of the treatment effects on microstructure and on constituents of fibres. 

Research paper thumbnail of Ethanol from lignocellulosic biomasses; Etanolo da biomasse lignocellulosiche. Produzione di etanolo da paglia di grano mediante pretrattamento di steam explosion, idrolisi enzimatica e fermentazione

In this report are presented results achieved on the process optimisation of bioethanol productio... more In this report are presented results achieved on the process optimisation of bioethanol production from wheat straw, carried out within the ENEA's project of biomass exploitation for renewable energy. The process consists of three main steps: 1) biomass pretreatment by means of steam explosion; 2) enzymatic hydrolysis of the cellulose fraction; 3) fermentation of glucose. To perform the hydrolysis step, two commercial enzymatic mixtures have been employed, mainly composed by {beta}-glucosidase (cellobiase), endo-glucanase and exo-glucanase. The ethanologenic yeast Saccharomyces cerevisiae has been used to ferment the glucose in he hydrolyzates. Hydrolysis yield of 97% has been obtained with steam exploded wheat straw treated at 220{sup 0}C for 3 minutes and an enzyme to substrate ratio of 4%. It has been pointed out the necessity of washing with water the pretreated what straw, in order to remove the biomass degradation products, which have shown an inhibition effect on the yeas...

Research paper thumbnail of Biomasse vegetali come fonte di energie rinnovabili: trattamenti integrati fisico- chimici e biotecnologici per migliorare l'idrolisi dei polisaccaridi nella produzione di bioetanolo

Dottorato di ricerca in ecologia fondamentale. 8. ciclo. Relatore P. De Leo. Coordinatore S. Marc... more Dottorato di ricerca in ecologia fondamentale. 8. ciclo. Relatore P. De Leo. Coordinatore S. MarchioriConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Research paper thumbnail of Biorefineries

Biofuels Production and Processing Technology, 2017

Research paper thumbnail of Ethanol Production in Immobilized-Cell Bioreactors from Mixed Sugar Syrups and Enzymatic Hydrolysates of Steam-Exploded Biomass

Applied Biochemistry and Biotechnology, 2004

We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzym... more We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzymatic saccharification of steam-pretreated aspen chips. Syrups containing 45 g/L of glucose and 12 g/L of xylose were detoxified through two ion-exchange resins and then fermented with Pichia stipitis and Saccharomyces cerevisiae immobilized in Ca-alginate gel beads. Combinations of different gel fractions in the fermentation volume, amount of yeast cells, and ratios of P. stipitis vs S. cerevisiae within each bead were compared. In the best conditions, by using a total beads volume corresponding to 25% of the working volume, we obtained a yield of 0.39 gethanol/ g initial sugars. This amount of gel entrapped an initial cell concentration of 6 × 10 12 cells/L with ratio of S. cerevisiae/P. stipitis of 0.25 g/g. Modified stirredtank reactors were obtained either by adding marbles or by inserting a perforated metal cylinder, which reduced considerably the rupture of beads while visibly improving oxygenation of the medium.

Research paper thumbnail of Steam Explosion of Straw in Batch and Continuous Systems

Applied Biochemistry and Biotechnology, 1999

The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat ... more The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat straw have been investigated. The treatments have been carried out in batch and continuous reactors with capacity of 0.5 Kg/cycle and 150 Kg/h, respectively. The exploded materials have been sequentially extracted with water at 65°C and sodium hydroxide 1.5%. Analytical determinations of liquid fractions and solid residues have led to the fractionation pattern of the carbohydrates as monomers, oligomers, and polymers. Evaluations of total acidity, ash content, and lignin recovery have improved understanding of the process. This part of the work has allowed us to derive: the empiric relationship between the batch and the continuous reactors and the yield and availability of pentoses and hexoses in various phases. Selected samples have been tested in enzymatic-hydrolysis experiments, pointing out the effect of treatment severity and reactor used on the saccharification yield.

Research paper thumbnail of The Role of Agrifood Organic Residues to Increase the Overall Sustainability of Mediterranean Diet

Research paper thumbnail of Biorefineries: Biofuels, Biochemicals, and Bioproducts

Research paper thumbnail of Gheorghe Asachi ” Technical University of Iasi , Romania P 69 BIOETHANOL PRODUCTION FROM MIXED SUGARS USING Scheffersomyces stipitis

Bioethanol can be produced from different biomasses, including lignocellulosic feedstocks, which ... more Bioethanol can be produced from different biomasses, including lignocellulosic feedstocks, which can contain comparable amounts of 5-carbon and 6-carbon sugars. In order to obtain an effective conversion of these biomass carbohydrates, suitable microorganisms are required for the fermentation step. In this paper the ability of Scheffersomyces stipitis to ferment mixed syrups has been investigated in pure culture and in co-cultures with other yeasts species. Both the performance of free and entrapped cells were explored. The performance of the Schef. stipitis strain NRRLY-11544, was initially tested by using synthetic broths containing different sugars concentrations, with a xylose fraction of 50%. According to the diauxic behavior of Schef. stipitis, the sugars consumption occurred sequentially, achieving an average process yield of 75%. To overcome this drawback, the cells immobilization was tested. Silica-hydrogel films and alginate beads were used as immobilization carriers. The ...

Research paper thumbnail of Continuous bioethanol production in immobilized cells fermentor coupled with a pervaporation system

In recent years, the research on bioethanol production from lignocellulosics has been mainly focu... more In recent years, the research on bioethanol production from lignocellulosics has been mainly focused on the optimization of single conversion steps while less attention has been devoted to the process integration. In some cases, depending on the specific composition of the biomass processed, the final ethanol concentration in the broth could feebly reach the target of 4 wt% considered acceptable for a subsequent economically feasible distillation. Thus, one possible integration that might be beneficial for the process is the use of immobilized cells bioreactor faced with a continuous ethanol stripping module. This process configuration would offer several advantages: the use of immobilized cell bioreactors yields high productivities and the catalyst entrapment within the bioreactor is more suitable for continuous operations; the ethanol removal guarantees a reduced yeast stress and the production of more concentrated streams prior to the distillation. In the present paper, the ferme...

Research paper thumbnail of IONIO Project: Computer-mediated Decision Support System and Communication in Ocean Science

Research paper thumbnail of Bioethanol production from mixed sugars by Scheffersomyces stipitis free and immobilized cells, and co-cultures with Saccharomyces cerevisiae

New Biotechnology, 2013

Bioethanol can be produced from several biomasses including lignocellulosic materials. Besides 6-... more Bioethanol can be produced from several biomasses including lignocellulosic materials. Besides 6-carbon sugars that represent the prevalent carbohydrates, some of these feedstocks contain significant amounts of 5-carbon sugars. One common limit of the major part of the xylose-fermenting yeasts is the diauxic shift between the uptake of glucose and xylose during the fermentation of mixed syrups. Thus, optimized fermentation strategies are required. In this paper the ability of Scheffersomyces stipitis strain NRRLY-11544 to ferment mixed syrups with a total sugar concentration in the range 40-80 g/L was investigated by using mono cultures, co-cultures with Saccharomyces cerevisiae strain Bakers Yeast Type II and single cultures immobilized in silica-hydrogel films. The experimental design for the fermentations with immobilized cells included the process analysis in function of two parameters: the fraction of the gel in the broth and the concentration of the cells loaded in the gel. Furthermore, for each total sugars level, the fermentative course of S. stipitis was analyzed at several glucose-to xylose ratios. The results indicated that the use of S. stipitis and S. cerevisiae in free co-cultures ensured faster processes than single cultures of S. stipitis either free or immobilized. However, the rapid production of ethanol by S. cerevisiae inhibited S. stipitis and caused a stuck of the process. Immobilization of S. stipitis in silica-hydrogel increased the relative consumption rate of xylose-to-glucose by 2-6 times depending on the composition of the fermentation medium. Furthermore the films performances appeared stable over three weeks of continuous operations. However, on the whole, the final process yields obtained with the immobilized cells were not meaningfully different from that of the free cells. This was probably due to concurrent fermentations operated by the cells released in the broth. Optimization of the carrier characteristics could improve the performances of the process with immobilized cells.

Research paper thumbnail of Bioethanol production from steam-pretreated corn stover through an isomerase mediated process

New Biotechnology, 2014

Agricultural by-products such as corn stover are considered strategic raw materials for the produ... more Agricultural by-products such as corn stover are considered strategic raw materials for the production of second-generation bioethanol from renewable and non-food sources. This paper describes the conversion of steam-pretreated corn stover to ethanol utilising a multi-step process including enzymatic hydrolysis, isomerisation, and fermentation of mixed hydrolysates with native Saccharomyces cerevisiae. An immobilised isomerase enzyme was used for the xylose isomerisation along with high concentrations of S. cerevisiae. The objective was to assess the extent of simultaneity of the various conversion steps, through a detailed analysis of process time courses, and to test this process scheme for the conversion of lignocellulosic hydrolysates containing several inhibitors of the isomerase enzyme (e.g. metal ions, xylitol and glycerol). The process was tested on two types of hydrolysate after acid-catalysed steam pretreatment: (a) the water soluble fraction (WSF) in which xylose was the largest carbon source and (b) the entire slurry, containing both cellulose and hemicellulose carbohydrates, in which glucose predominated. The results indicated that the ethanol concentration rose when the inoculum concentration was increased in the range 10-75 g/L. However, when xylose was the largest carbon source, the metabolic yields were higher than 0.51 g ethanol /g consumed sugars probably due to the use of yeast internal cellular resources. This phenomenon was not observed in the fermentation of mixed hydrolysates obtained from the entire pretreated product and in which glucose was the largest carbon source. The ethanol yield from biomass suspensions with dry matter (DM) concentrations of 11-12% (w/v) was 70% based on total sugars (glucose, xylose, galactose). The results suggest that xylulose uptake was more effective in mixed hydrolysates containing glucose levels similar to, or higher than, xylose. Analysis of the factors that limit isomerase activity in lignocellulosic hydrolysates excluded any inhibition due to residual calcium ions after the detoxification of the hemicellulose hydrolysates with Ca(OH) 2 . By contrast, most of the enzyme activity ceased during the fermentation of the entire slurry after steam explosion, probably due to synergistic inhibition effects of various fermentation coproducts.

Research paper thumbnail of Ethanol Production in Immobilized-Cell Bioreactors from Mixed Sugar Syrups and Enzymatic Hydrolysates of Steam-Exploded Biomass

Applied Biochemistry and Biotechnology, 2004

We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzym... more We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzymatic saccharification of steam-pretreated aspen chips. Syrups containing 45 g/L of glucose and 12 g/L of xylose were detoxified through two ion-exchange resins and then fermented with Pichia stipitis and Saccharomyces cerevisiae immobilized in Ca-alginate gel beads. Combinations of different gel fractions in the fermentation volume, amount of yeast cells, and ratios of P. stipitis vs S. cerevisiae within each bead were compared. In the best conditions, by using a total beads volume corresponding to 25% of the working volume, we obtained a yield of 0.39 gethanol/ g initial sugars . This amount of gel entrapped an initial cell concentration of 6 × 10 12 cells/L with ratio of S. cerevisiae/P. stipitis of 0.25 g/g. Modified stirredtank reactors were obtained either by adding marbles or by inserting a perforated metal cylinder, which reduced considerably the rupture of beads while visibly improving oxygenation of the medium.

Research paper thumbnail of Steam Explosion of Straw in Batch and Continuous Systems

Applied Biochemistry and Biotechnology, 1999

The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat ... more The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat straw have been investigated. The treatments have been carried out in batch and continuous reactors with capacity of 0.5 Kg/cycle and 150 Kg/h, respectively. The exploded materials have been sequentially extracted with water at 65°C and sodium hydroxide 1.5%. Analytical determinations of liquid fractions and solid residues have led to the fractionation pattern of the carbohydrates as monomers, oligomers, and polymers. Evaluations of total acidity, ash content, and lignin recovery have improved understanding of the process. This part of the work has allowed us to derive: the empiric relationship between the batch and the continuous reactors and the yield and availability of pentoses and hexoses in various phases. Selected samples have been tested in enzymatic-hydrolysis experiments, pointing out the effect of treatment severity and reactor used on the saccharification yield.

Research paper thumbnail of Biorefineries

Research paper thumbnail of Electrophoretic Deposition of Lignin Reinforced Polymer Coatings

Key Engineering Materials, Jul 1, 2015

Composite coatings based on PEEK and Lignin were obtained by EPD. The addition of Lignin had some... more Composite coatings based on PEEK and Lignin were obtained by EPD. The addition of Lignin had some beneficial effects, the most relevant being an increased coating adhesion on conductive substrates. Before using in EPD suspensions, Lignin was functionalised by a carbonyl group. This functionalisation produced chemical interactions between PEEK powder and Lignin, and, as a consequence, better results in terms of both EPD efficiency and adhesion coating. Moreover, the addition of Lignin increased the hydrophobicity of PEEK coatings when they were thermally treated at temperature lower than the melting point of PEEK.

Research paper thumbnail of Bioethanol production from steam-pretreated corn stover through an isomerase mediated process

New Biotechnology, Mar 1, 2014

Agricultural by-products such as corn stover are considered strategic raw materials for the produ... more Agricultural by-products such as corn stover are considered strategic raw materials for the production of second-generation bioethanol from renewable and non-food sources. This paper describes the conversion of steam-pretreated corn stover to ethanol utilising a multi-step process including enzymatic hydrolysis, isomerisation, and fermentation of mixed hydrolysates with native Saccharomyces cerevisiae. An immobilised isomerase enzyme was used for the xylose isomerisation along with high concentrations of S. cerevisiae. The objective was to assess the extent of simultaneity of the various conversion steps, through a detailed analysis of process time courses, and to test this process scheme for the conversion of lignocellulosic hydrolysates containing several inhibitors of the isomerase enzyme (e.g. metal ions, xylitol and glycerol). The process was tested on two types of hydrolysate after acid-catalysed steam pretreatment: (a) the water soluble fraction (WSF) in which xylose was the largest carbon source and (b) the entire slurry, containing both cellulose and hemicellulose carbohydrates, in which glucose predominated. The results indicated that the ethanol concentration rose when the inoculum concentration was increased in the range 10-75 g/L. However, when xylose was the largest carbon source, the metabolic yields were higher than 0.51 g ethanol /g consumed sugars probably due to the use of yeast internal cellular resources. This phenomenon was not observed in the fermentation of mixed hydrolysates obtained from the entire pretreated product and in which glucose was the largest carbon source. The ethanol yield from biomass suspensions with dry matter (DM) concentrations of 11-12% (w/v) was 70% based on total sugars (glucose, xylose, galactose). The results suggest that xylulose uptake was more effective in mixed hydrolysates containing glucose levels similar to, or higher than, xylose. Analysis of the factors that limit isomerase activity in lignocellulosic hydrolysates excluded any inhibition due to residual calcium ions after the detoxification of the hemicellulose hydrolysates with Ca(OH) 2. By contrast, most of the enzyme activity ceased during the fermentation of the entire slurry after steam explosion, probably due to synergistic inhibition effects of various fermentation coproducts.

Research paper thumbnail of Chlorinated hydrocarbons and heavy metals in tissues of Striped dolphin (Stenella coeruleoalba) stranded along the Apulian and Sicilian coasts (Summer 1991)

Research paper thumbnail of Alternative exploitation of Cynara spp. biodiversity in a bioeconomy context

Research paper thumbnail of Effect of treatments on the aging behaviour of hemp fibres for building construction in the Mediterranean Area

Journal of Building Engineering, 2017

The aim of this work is to study the influence of selected treatments on the behaviour of hemp fi... more The aim of this work is to study the influence of selected treatments on the behaviour of hemp fibres when used as insulation material in building envelopes, with particular regard to construction in the Mediterranean Area. In particular, the effects of treatments with salicylic acid and a natural monoterpenes phenol, for enhancing the resistance to degradation of hemp fibres to microbial attacks, were evaluated. Several types of hemp mats were prepared and contaminated with two fungal microorganisms and then subjected to accelerated weathering cycles in a climatic chamber, together with a hollow brick whose some holes were filled with chemically treated and untreated fibres. The experiment pointed out that, within the duration of the two-months long accelerated weathering test, simulating one year of service life in Mediterranean Area, neither fungal contamination nor significant changes in mass, colour and visual appearance, as well as structural properties and morphology, were observed for both the treated and untreated fibres. Nevertheless, the trend of temperatures and relative humidity realized inside the filled holes of the hollow brick underlined that the treated fibres showed a lower capacity to adsorb and desorb moisture with respect to untreated fibres. This behaviour is considered favourable, because it reduces the risk of moisture retention giving, in principle, advantages in terms of deterioration and resistance of the fibres to fungal attack. The differences of behaviour between treated and untreated hemp mats were investigated through XRD and FTIR analysis which revealed that the former had higher crystallinity and therefore lower capacity to uptake water. Highlights  accelerated weathering test on Mediterranean Area;  hemp fibres as insulating materials in Mediterranean Area;  Influence of treatments with natural substances on hygro-thermal behaviour of hemp fibres;  Evaluation of the treatment effects on microstructure and on constituents of fibres. 

Research paper thumbnail of Ethanol from lignocellulosic biomasses; Etanolo da biomasse lignocellulosiche. Produzione di etanolo da paglia di grano mediante pretrattamento di steam explosion, idrolisi enzimatica e fermentazione

In this report are presented results achieved on the process optimisation of bioethanol productio... more In this report are presented results achieved on the process optimisation of bioethanol production from wheat straw, carried out within the ENEA's project of biomass exploitation for renewable energy. The process consists of three main steps: 1) biomass pretreatment by means of steam explosion; 2) enzymatic hydrolysis of the cellulose fraction; 3) fermentation of glucose. To perform the hydrolysis step, two commercial enzymatic mixtures have been employed, mainly composed by {beta}-glucosidase (cellobiase), endo-glucanase and exo-glucanase. The ethanologenic yeast Saccharomyces cerevisiae has been used to ferment the glucose in he hydrolyzates. Hydrolysis yield of 97% has been obtained with steam exploded wheat straw treated at 220{sup 0}C for 3 minutes and an enzyme to substrate ratio of 4%. It has been pointed out the necessity of washing with water the pretreated what straw, in order to remove the biomass degradation products, which have shown an inhibition effect on the yeas...

Research paper thumbnail of Biomasse vegetali come fonte di energie rinnovabili: trattamenti integrati fisico- chimici e biotecnologici per migliorare l'idrolisi dei polisaccaridi nella produzione di bioetanolo

Dottorato di ricerca in ecologia fondamentale. 8. ciclo. Relatore P. De Leo. Coordinatore S. Marc... more Dottorato di ricerca in ecologia fondamentale. 8. ciclo. Relatore P. De Leo. Coordinatore S. MarchioriConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Research paper thumbnail of Biorefineries

Biofuels Production and Processing Technology, 2017

Research paper thumbnail of Ethanol Production in Immobilized-Cell Bioreactors from Mixed Sugar Syrups and Enzymatic Hydrolysates of Steam-Exploded Biomass

Applied Biochemistry and Biotechnology, 2004

We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzym... more We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzymatic saccharification of steam-pretreated aspen chips. Syrups containing 45 g/L of glucose and 12 g/L of xylose were detoxified through two ion-exchange resins and then fermented with Pichia stipitis and Saccharomyces cerevisiae immobilized in Ca-alginate gel beads. Combinations of different gel fractions in the fermentation volume, amount of yeast cells, and ratios of P. stipitis vs S. cerevisiae within each bead were compared. In the best conditions, by using a total beads volume corresponding to 25% of the working volume, we obtained a yield of 0.39 gethanol/ g initial sugars. This amount of gel entrapped an initial cell concentration of 6 × 10 12 cells/L with ratio of S. cerevisiae/P. stipitis of 0.25 g/g. Modified stirredtank reactors were obtained either by adding marbles or by inserting a perforated metal cylinder, which reduced considerably the rupture of beads while visibly improving oxygenation of the medium.

Research paper thumbnail of Steam Explosion of Straw in Batch and Continuous Systems

Applied Biochemistry and Biotechnology, 1999

The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat ... more The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat straw have been investigated. The treatments have been carried out in batch and continuous reactors with capacity of 0.5 Kg/cycle and 150 Kg/h, respectively. The exploded materials have been sequentially extracted with water at 65°C and sodium hydroxide 1.5%. Analytical determinations of liquid fractions and solid residues have led to the fractionation pattern of the carbohydrates as monomers, oligomers, and polymers. Evaluations of total acidity, ash content, and lignin recovery have improved understanding of the process. This part of the work has allowed us to derive: the empiric relationship between the batch and the continuous reactors and the yield and availability of pentoses and hexoses in various phases. Selected samples have been tested in enzymatic-hydrolysis experiments, pointing out the effect of treatment severity and reactor used on the saccharification yield.

Research paper thumbnail of The Role of Agrifood Organic Residues to Increase the Overall Sustainability of Mediterranean Diet

Research paper thumbnail of Biorefineries: Biofuels, Biochemicals, and Bioproducts

Research paper thumbnail of Gheorghe Asachi ” Technical University of Iasi , Romania P 69 BIOETHANOL PRODUCTION FROM MIXED SUGARS USING Scheffersomyces stipitis

Bioethanol can be produced from different biomasses, including lignocellulosic feedstocks, which ... more Bioethanol can be produced from different biomasses, including lignocellulosic feedstocks, which can contain comparable amounts of 5-carbon and 6-carbon sugars. In order to obtain an effective conversion of these biomass carbohydrates, suitable microorganisms are required for the fermentation step. In this paper the ability of Scheffersomyces stipitis to ferment mixed syrups has been investigated in pure culture and in co-cultures with other yeasts species. Both the performance of free and entrapped cells were explored. The performance of the Schef. stipitis strain NRRLY-11544, was initially tested by using synthetic broths containing different sugars concentrations, with a xylose fraction of 50%. According to the diauxic behavior of Schef. stipitis, the sugars consumption occurred sequentially, achieving an average process yield of 75%. To overcome this drawback, the cells immobilization was tested. Silica-hydrogel films and alginate beads were used as immobilization carriers. The ...

Research paper thumbnail of Continuous bioethanol production in immobilized cells fermentor coupled with a pervaporation system

In recent years, the research on bioethanol production from lignocellulosics has been mainly focu... more In recent years, the research on bioethanol production from lignocellulosics has been mainly focused on the optimization of single conversion steps while less attention has been devoted to the process integration. In some cases, depending on the specific composition of the biomass processed, the final ethanol concentration in the broth could feebly reach the target of 4 wt% considered acceptable for a subsequent economically feasible distillation. Thus, one possible integration that might be beneficial for the process is the use of immobilized cells bioreactor faced with a continuous ethanol stripping module. This process configuration would offer several advantages: the use of immobilized cell bioreactors yields high productivities and the catalyst entrapment within the bioreactor is more suitable for continuous operations; the ethanol removal guarantees a reduced yeast stress and the production of more concentrated streams prior to the distillation. In the present paper, the ferme...

Research paper thumbnail of IONIO Project: Computer-mediated Decision Support System and Communication in Ocean Science

Research paper thumbnail of Bioethanol production from mixed sugars by Scheffersomyces stipitis free and immobilized cells, and co-cultures with Saccharomyces cerevisiae

New Biotechnology, 2013

Bioethanol can be produced from several biomasses including lignocellulosic materials. Besides 6-... more Bioethanol can be produced from several biomasses including lignocellulosic materials. Besides 6-carbon sugars that represent the prevalent carbohydrates, some of these feedstocks contain significant amounts of 5-carbon sugars. One common limit of the major part of the xylose-fermenting yeasts is the diauxic shift between the uptake of glucose and xylose during the fermentation of mixed syrups. Thus, optimized fermentation strategies are required. In this paper the ability of Scheffersomyces stipitis strain NRRLY-11544 to ferment mixed syrups with a total sugar concentration in the range 40-80 g/L was investigated by using mono cultures, co-cultures with Saccharomyces cerevisiae strain Bakers Yeast Type II and single cultures immobilized in silica-hydrogel films. The experimental design for the fermentations with immobilized cells included the process analysis in function of two parameters: the fraction of the gel in the broth and the concentration of the cells loaded in the gel. Furthermore, for each total sugars level, the fermentative course of S. stipitis was analyzed at several glucose-to xylose ratios. The results indicated that the use of S. stipitis and S. cerevisiae in free co-cultures ensured faster processes than single cultures of S. stipitis either free or immobilized. However, the rapid production of ethanol by S. cerevisiae inhibited S. stipitis and caused a stuck of the process. Immobilization of S. stipitis in silica-hydrogel increased the relative consumption rate of xylose-to-glucose by 2-6 times depending on the composition of the fermentation medium. Furthermore the films performances appeared stable over three weeks of continuous operations. However, on the whole, the final process yields obtained with the immobilized cells were not meaningfully different from that of the free cells. This was probably due to concurrent fermentations operated by the cells released in the broth. Optimization of the carrier characteristics could improve the performances of the process with immobilized cells.

Research paper thumbnail of Bioethanol production from steam-pretreated corn stover through an isomerase mediated process

New Biotechnology, 2014

Agricultural by-products such as corn stover are considered strategic raw materials for the produ... more Agricultural by-products such as corn stover are considered strategic raw materials for the production of second-generation bioethanol from renewable and non-food sources. This paper describes the conversion of steam-pretreated corn stover to ethanol utilising a multi-step process including enzymatic hydrolysis, isomerisation, and fermentation of mixed hydrolysates with native Saccharomyces cerevisiae. An immobilised isomerase enzyme was used for the xylose isomerisation along with high concentrations of S. cerevisiae. The objective was to assess the extent of simultaneity of the various conversion steps, through a detailed analysis of process time courses, and to test this process scheme for the conversion of lignocellulosic hydrolysates containing several inhibitors of the isomerase enzyme (e.g. metal ions, xylitol and glycerol). The process was tested on two types of hydrolysate after acid-catalysed steam pretreatment: (a) the water soluble fraction (WSF) in which xylose was the largest carbon source and (b) the entire slurry, containing both cellulose and hemicellulose carbohydrates, in which glucose predominated. The results indicated that the ethanol concentration rose when the inoculum concentration was increased in the range 10-75 g/L. However, when xylose was the largest carbon source, the metabolic yields were higher than 0.51 g ethanol /g consumed sugars probably due to the use of yeast internal cellular resources. This phenomenon was not observed in the fermentation of mixed hydrolysates obtained from the entire pretreated product and in which glucose was the largest carbon source. The ethanol yield from biomass suspensions with dry matter (DM) concentrations of 11-12% (w/v) was 70% based on total sugars (glucose, xylose, galactose). The results suggest that xylulose uptake was more effective in mixed hydrolysates containing glucose levels similar to, or higher than, xylose. Analysis of the factors that limit isomerase activity in lignocellulosic hydrolysates excluded any inhibition due to residual calcium ions after the detoxification of the hemicellulose hydrolysates with Ca(OH) 2 . By contrast, most of the enzyme activity ceased during the fermentation of the entire slurry after steam explosion, probably due to synergistic inhibition effects of various fermentation coproducts.

Research paper thumbnail of Ethanol Production in Immobilized-Cell Bioreactors from Mixed Sugar Syrups and Enzymatic Hydrolysates of Steam-Exploded Biomass

Applied Biochemistry and Biotechnology, 2004

We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzym... more We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzymatic saccharification of steam-pretreated aspen chips. Syrups containing 45 g/L of glucose and 12 g/L of xylose were detoxified through two ion-exchange resins and then fermented with Pichia stipitis and Saccharomyces cerevisiae immobilized in Ca-alginate gel beads. Combinations of different gel fractions in the fermentation volume, amount of yeast cells, and ratios of P. stipitis vs S. cerevisiae within each bead were compared. In the best conditions, by using a total beads volume corresponding to 25% of the working volume, we obtained a yield of 0.39 gethanol/ g initial sugars . This amount of gel entrapped an initial cell concentration of 6 × 10 12 cells/L with ratio of S. cerevisiae/P. stipitis of 0.25 g/g. Modified stirredtank reactors were obtained either by adding marbles or by inserting a perforated metal cylinder, which reduced considerably the rupture of beads while visibly improving oxygenation of the medium.

Research paper thumbnail of Steam Explosion of Straw in Batch and Continuous Systems

Applied Biochemistry and Biotechnology, 1999

The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat ... more The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat straw have been investigated. The treatments have been carried out in batch and continuous reactors with capacity of 0.5 Kg/cycle and 150 Kg/h, respectively. The exploded materials have been sequentially extracted with water at 65°C and sodium hydroxide 1.5%. Analytical determinations of liquid fractions and solid residues have led to the fractionation pattern of the carbohydrates as monomers, oligomers, and polymers. Evaluations of total acidity, ash content, and lignin recovery have improved understanding of the process. This part of the work has allowed us to derive: the empiric relationship between the batch and the continuous reactors and the yield and availability of pentoses and hexoses in various phases. Selected samples have been tested in enzymatic-hydrolysis experiments, pointing out the effect of treatment severity and reactor used on the saccharification yield.