Bioconversion Of Starch Research Articles

The use of immobilized enzyme in starch bioconversion: An update review

Starch bioconversion enzymes play an important role in the food industry, raising up a vast research space. Immobilization of alpha-amylase, amyloglucosidase and glucose isomerase is a promising topic for ongoing research. In this review, we provide an updated overview of various carriers for carbohydrases immobilization, with the primary focus on the food industry. The method used in this review is the literature study method. The immobilization methods of carbohydrases enzymes are encapsulation by Ca-alginate, covalent and ionic bonding by chitosan, adsorption by ion exchange resin and cross-linking by glutaraldehyde and Bovine serum albumin as protein feeder, and mix of them. The research shows the ability of enzymes that can be used repeatedly while maintaining their activity. Immobilization increases the enzymes stability towards pH, temperature, and type of substrate. Through this method, various types of sugar such as maltose, glucose and fructose can be produced with reduced production costs. In future, immobilized enzymes are going to play a vital role in various industries not only in food, but including pharmaceuticals, chemicals, and fuel.

Computational Insights into the Selecting Mechanism of α-Amylase Immobilized on Cellulose Nanocrystals: Unveiling the Potential of α-Amylases Immobilized for Efficient Poultry Feed Hydrolysis.

The selection of an appropriate amylase for hydrolysis poultry feed is crucial for achieving improved digestibility and high-quality feed. Cellulose nanocrystals (CNCs), which are known for their high surface area, provide an excellent platform for enzyme immobilization. Immobilization greatly enhances the operational stability of α-amylases and the efficiency of starch bioconversion in poultry feeds. In this study, we immobilized two metagenome-derived α-amylases, PersiAmy2 and PersiAmy3, on CNCs and employed computational methods to characterize and compare the degradation efficiencies of these enzymes for poultry feed hydrolysis. Experimental in vitro bioconversion assessments were performed to validate the computational outcomes. Molecular docking studies revealed the superior hydrolysis performance of PersiAmy3, which displayed stronger electrostatic interactions with CNCs. Experimental characterization demonstrated the improved performance of both α-amylases after immobilization at high temperatures (80 °C). A similar trend was observed under alkaline conditions, with α-amylase activity reaching 88% within a pH range of 8.0 to 9.0. Both immobilized α-amylases exhibited halotolerance at NaCl concentrations up to 3 M and retained over 50% of their initial activity after 13 use cycles. Notably, PersiAmy3 displayed more remarkable improvements than PersiAmy2 following immobilization, including a significant increase in activity from 65 to 80.73% at 80 °C, an increase in activity to 156.48% at a high salinity of 3 M NaCl, and a longer half-life, indicating greater thermal stability within the range of 60 to 80 °C. These findings were substantiated by the in vitro hydrolysis of poultry feed, where PersiAmy3 generated 53.53 g/L reducing sugars. This comprehensive comparison underscores the utility of computational methods as a faster and more efficient approach for selecting optimal enzymes for poultry feed hydrolysis, thereby providing valuable insights into enhancing feed digestibility and quality.

Effect of the stirring speed in the in vitro activity of α-amylase

Amylases are one of the main enzymes used in industry for hydrolyzing starch molecules into simple sugar constituents, can be sourced from plants, animals and microorganisms. Starch converting α-amylase has applications in different industrial sectors, and an ongoing research topic is to improve processing conditions leading to enhanced enzymatic activity and lower processing costs. Surprisingly, there are basically no studies regarding the impact of stirring speed on α-amylase activity. In this work, the effect of stirring speed (0, 50, 250, 500, 1000 and 1500 rpm) on the hydrolysis of gelatinized corn starch dispersions (5 g starch dry basis/100 L) by pancreatic α-amylase (0.125 and 0.250 μg/mL) was studied. The analysis of the hydrolysis kinetics curves showed that relatively small stirring speeds had positive effect on the hydrolysis rate. This effect was likely caused by improvements in the mass transfer coefficient by virtue of increased flow velocities. However, the enzyme activity exhibited a negative trend for high stirring speeds. FTIR analysis of α-amylase subjected to stirring indicated that changes in the Amide I secondary structure might be behind the decreased hydrolysis at high stirring speeds. This short communication provides insights for enhancing the bio-conversion of starch by α-amylase via stirring speed mediation.

Valorisation of restaurant food waste under the concept of a biorefinery

This paper explores the challenge to turn restaurant food waste from environmental issue to energy asset. The transformation of the dehydrated restaurant food waste to used oil, ethanol and methane was investigated. Each process unit was studied and optimised. Thermal dehydration was adopted producing a dried feedstock suitable for the downstream processes as well as a condensate rich in volatile fatty acids with a biomethane potential yield of 1.24 L CH4/L. In the oil extraction process, the application of hexane, 20 Soxhlet cycles and solvent to feedstock ratio equal to 2 provided 81.76% oil yield with quality suitable for transesterification. Different loadings of non-commercial amylolytic enzyme were examined so as to enhance the starch bioconversion efficiency. Five microlitres of enzyme per gramme of starch and 90 min of saccharification time were selected as the optimum operating conditions for producing a hydrolysate that could be efficiently fermented to ethanol. The anaerobic biodegradability of the resulting stillage (415 L CH4/kg VS) could further promote the viability of the whole treatment train. The experimental results were integrated in a material flow diagram in order to enlighten the assessment of the biorefinery scheme.

Autodisplay of alpha amylase from Bacillus megaterium in E. coli for the bioconversion of starch into hydrogen, ethanol and succinic acid

In this work, the expression of an α-amylase from Bacillus megaterium on the cell surface of Escherichia coli strains WDHA (Δ hycA and Δ ldhA) and WDHFP (Δ hycA, Δ frdD and Δ pta) by the autodisplay adhesin involved in diffuse adherence (AIDA) system was carried out with the purpose to confer the ability to E. coli strains to degrade starch and thus produce hydrogen, ethanol and succinic acid. For the characterization of the biocatalyst, the effect of temperature (30−70 °C), pH (3–6) and CaCl2 concentration (0−25 mM), as well as the thermostability of the biocatalyst (55−80 °C) at several time intervals (15−60 min) were evaluated. The results showed that the biocatalyst had a maximum activity at 55 °C and pH 4.5. Calcium was required for the activity as well for the thermal stability of the biocatalyst. The calculated Vmax and Km values were 0.24 U/cm3 and 5.8 mg/cm3, respectively. Furthermore, a set of anaerobic batch fermentations was carried out using 10 g/dm3 of starch and 1 g/dm3 of glucose as carbon sources in 120 cm3 serological bottles, using WDHA and WDHFP strains harboring the pAIDA-amyA plasmid. The hydrogen production for WDHA was 1056.06 cm3/dm3 and the succinic acid yield was 0.68 g/gstarch, whereas WDHFP strain produced 1689.68 cm3/dm3 of hydrogen and an ethanol yield of 0.28 g/gstarch. This work represents a promising strategy to improve the exploitation of starchy biomass for the production of biofuels (hydrogen and ethanol) or succinate without the need of a pre-saccharification process.

Response of morphology and microbial community structure of granules to influent COD/SO42 – ratios in an upflow anaerobic sludge blanket (UASB) reactor treating starch wastewater

Biochemical properties of granules are of vital importance to UASB performance. This study characterized the granules cultivated at different COD/SO42− ratios to elucidate the influence of sulfidogenesis on starch wastewater (1000 mg-COD L−1) biodegradation kinetics and process stability. Suitable sulfate addition enriched granular microecosystems and stimulated the secretion of extracellular substances, facilitating cells cohersion and sludge aggregation. The percentage of granules larger than 2.8 mm increased from <10.0% to 58.8–69.4% with decreasing COD/SO42− ratio from 10 to 2. Starch-fed granules tended to grow flagella-like filaments on the surface. The filaments overwhelmed by hydrophilic biopolymers had high affinity for biogas-bubbles and water-molecules aggravating granule floatation and washout. 16 s rRNA gene analysis revealed that decreasing COD/SO42− ratio shifted Syntrophobacterales to Desulfovibrio, which co-worked with Methanosaeta while suppressing Methanobacterium thereby altering starch bioconversion routes. Decrease in Syntrophobacterales caused propionate accumulation and slight process upset.

Modeling the bioconversion of starch to P(HB-co-HV) optimized by experimental design using Bacillus megaterium BBST4 strain

ABSTRACTPoly(hydroxybutyrate-co-hydroxyvalerate) (P(HB-co-HV)) is a prominent biopolymer as a potential candidate for use in the biomedical area. Several Bacillus spp. strains show promising characteristics in the use of several carbon sources and are an interesting alternative for the production of P(HB-co-HV). Sewage from the agricultural and food processing industries can be used to obtain abundantly starch as a carbon source for PHA production. The aim of the present study was to optimize by response surface methodology and desirability, the production of PHA by a Bacillus megaterium strain using starch as the sole carbon source. Two optimal conditions were determined without sporulation and were used to perform new experiments to calibrate and validate a mechanistic model, developed to simulate the dynamics of PHA and biomass production. The developed model successfully represents the kinetics of the microorganism. Employing different characterization techniques, it was determined that the PHA produced by the strain is a copolymer composed of different HB:HV proportions. Using starch as the sole carbon source in a minimal salt medium, this work shows the first reports in the literature of: 1) a mathematical model for predicting growth kinetic and PHA production for B. megaterium strain and 2) a Bacillus spp. producing P(HB-co-HV) copolymer.

High efficacy bioconversion of starch to lactic acid using an amylolytic lactic acid bacterium isolated from Thai indigenous fermented rice noodles

Amylolytic lactic acid bacterium (ALAB) strain S21 was isolated from Thai indigenous fermented rice noodles and identified as Lactobacillus plantarum, based on 16S rDNA sequence and recA gene analysis. L. plantarum S21 exhibited a specific growth rate (μ) of 0.24 1/h in modified MRS broth containing 10 g/L of starch as the sole carbon source, and a high efficacy in producing lactic acid (9.41, 24.48, 41.84, 74.33, and 94.04 g/L from 10, 25, 50, 75, and 100 g/L of cassava starch, respectively), which are higher values than previously reported for ALAB. Crude amylase from L. plantarum S21 had broad pH stability (3.5–8.0), and hydrolyzed starch to maltose and glucose as the major and minor products. L. plantarum S21 should be considered useful for industrial bioconversion of starch to lactic acid.

Effect of organic solvents on the yield and specificity of cyclodextrins by recombinant cyclodextrin glucanotransferase (CGTase) from Anaerobranca gottschalkii

Cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) is an enzyme that degrades starch and starch related glucans into cyclodextrins (CDs) by intramolecular transglycosylation reaction. The biochemical activity of recombinant CGTase from Anaerobranca gottschalkii for the yield and product specificity of cyclodextrins was investigated in the presence of organic solvents. Compared with the control of starch bioconversion, addition of various organic solvents generally increased the total CD and product specificity by affecting product inhibition and/or intermolecular transglycosylation reaction. The highest conversion (45 %) of starch to CDs was obtained in the presence of ethanol, while the simultaneous addition of two organic solvents, decanol-ethanol, comparatively showed a reduced total yield of 39 %. Despite this, the highest product ratio of 91 % α-CD, and 64 % β-CD was obtained in the presence of decanol and cyclohexane respectively. The effect of organic solvents on the yield and specificity of CD was attributed mainly to their effect on product inhibition and transglycosylation reaction. Although the use of two organic solvents showed almost a significant increase in total yield of CDs, it resulted in a comparatively lower specific product yield compared to their respective individual effect. Generally, normal enzyme activity was favoured at higher temperature of 65 °C, but the addition of organic solvents, in most cases, was found to decrease the bioconversion. Thus, the preferred optimal condition was reduced to 40 °C, where the maximal conversion of starch to CDs in general and α-CD in particular was achieved.

Design of a knowledge and management system for starch bioconversion

In this paper a knowledge acquisition and management system (KAMS) which allows the collection, analysis, ordering and storage of informations generated at starch liquefaction was developed. KAMS was structured on three levels: PostgreSQL as a backend, D2RQ as middle tier and Seaside as frontend. The system was used to store knowledge about the liquefaction process with the goal to be used as a decision support system in chosing the condition for this operation. The tests had shown that the implemented KAMS provides support for: Distributed acquisition of the scientific data generated by the researchers; Structured data storage; Support for the generation and storage of knowledge on the starch bioconversion.

125th Anniversary Review: Fuel Alcohol: Current Production and Future Challenges

Global research and industrial development of liquid transportation biofuels are moving at a rapid pace. This is mainly due to the significant roles played by biofuels in decarbonising our future energy needs, since they act to mitigate the deleterious impacts of greenhouse gas emissions to the atmosphere that are contributors of climate change. Governmental obligations and international directives that mandate the blending of biofuels in petrol and diesel are also acting as great stimuli to this expanding industrial sector. Currently, the predominant liquid biofuel is bioethanol (fuel alcohol) and its worldwide production is dominated by maize-based and sugar cane-based processes in North and South America, respectively. In Europe, fuel alcohol production employs primarily wheat and sugar beet. Potable distilled spirit production and fuel alcohol processes share many similarities in terms of starch bioconversion, fermentation, distillation and co-product utilisation, but there are some key differences. For example, in certain bioethanol fermentations, it is now possible to yield consistently high ethanol concentrations of ˜20% (v/v). Emerging fuel alcohol processes exploit lignocellulosic feedstocks and scientific and technological constraints involved in depolymerising these materials and efficiently fermenting the hydrolysate sugars are being overcome. These so-called second-generation fuel alcohol processes are much more environmentally and ethically acceptable compared with exploitation of starch and sugar resources, especially when considering utilisation of residual agricultural biomass and biowastes. This review covers both first and second-generation bioethanol processes with a focus on current challenges and future opportunities of lignocellulose-to-ethanol as this technology moves from demonstration pilot-plants to full-scale industrial facilities.

Development of new unstructured model for simultaneous saccharification and fermentation of starch to ethanol by recombinant strain

The development of simultaneous saccharification and fermentation of starch to ethanol (SSFSE) by genetically modified microbial strains has been studied intensively [M.M. Altintas, B. Kirdar, Z.Ï. Önsan, K.Ö. Ülgen, Cybernetic modelling of growth and ethanol production in a recombinant Saccharomyces cerevisiae strain secreting a bifunctional fusion protein, Process Biochem. 37 (2002) 1439–1445; G. Birol, Z.Ï. Önsan, B. Kirdar, S.G. Oliver, Ethanol production and fermentation characteristics of recombinant Saccharomyces cerevisiae strains grown on starch, Enzyme Microb. Technol. 22 (1998) 672–677; F. Kobayashi, Y. Nakamura, Effect of repressor gene on stability of bioprocess with continuous conversion of starch into ethanol using recombinant yeast, Biochem. Eng. J. 18 (2004) 133–141; F. Kobayashi, Y. Nakamura, Mathematical model of direct ethanol production from starch in immobilized recombinant yeast culture, Biochem. Eng. J. 21 (2004) 93–101; M.M. Altintas, K.Ö. Ülgen, B. Kirdar, Z.Ï. Önsan, S.G. Oliver, Improvement of ethanol production from starch by recombinant yeast through manipulation of environmental factors, Enzyme Microb. Technol. 31 (2002) 640–647; K.Ö. Ülgen, B. Saygili, Z.Ï. Önsan, B. Kirdar, Bioconversion of starch into ethanol by a recombinant Saccharomyces cerevisiae strain YPG-AB, Process Biochem. 37 (2002) 1157–1168]. Saccharomyces cerevisiae YPB-G strain secretes a bifunctional fusion protein containing enzymatic activity of the B. subtilis alpha-amylase and of the Aspergillus awamori glucoamylase [M.M. Altintas, B. Kirdar, Z.Ï. Önsan, K.Ö. Ülgen, Cybernetic modelling of growth and ethanol production in a recombinant Saccharomyces cerevisiae strain secreting a bifunctional fusion protein, Process Biochem. 37 (2002) 1439–1445], and therefore is distinguished in relation to SSFSE step. In this work we have used the experimental data, presented in the paper [M.M. Altintas, B. Kirdar, Z.Ï. Önsan, K.Ö. Ülgen, Cybernetic modelling of growth and ethanol production in a recombinant Saccharomyces cerevisiae strain secreting a bifunctional fusion protein, Process Biochem. 37 (2002) 1439–1445] to develop two-hierarchic-level unstructured mathematical model describing kinetics of direct bioconversion of starch to ethanol. The first level has modeled enzymatic hydrolysis of starch to glucose by bifunctional protein and the second level includes utilization and bioconversion of glucose to ethanol by yeasts. The second level has unified the enzymatic degradation of starch, and glucose metabolization to ethanol by microorganisms. The response surface analysis was used to develop the rates models. A hybrid genetic algorithm and a decomposition approach were used in the nonlinear parameters identification procedure. The proposed model demonstrated excellent flexibility for different operational conditions of SSFSE process, and can be used successfully to describe microbial physiology of genetically modified strains.

Production of β-cyclodextrin: Effect of pH, time and additives

In the present paper attempt was made to produce an excipient, β-cyclodextrin from starch by the action of an enzyme cyclodextrin glucosyl transferase. The microbial strain utilized was Bacillus circulans because of its specificity for production of β-cyclodextrin. First the culture was grown under controlled conditions to obtain an enzyme cyclodextrin glucosyl transferase which was isolated and purified. The crude enzyme was employed for bioconversion of starch to β-cyclodextrin. Some parameters like incubation pH, incubation and fermentation time and effect of certain additives like polyethylene glycol and calcium chloride added during incubation were studied to optimize its yield. The maximum yield of cyclodextrin glucosyl transferase was after 36 h of fermentation. β-cyclodextrin yield was found to increase with the increase in incubation period, by the addition of polyethylene glycol 200, polyethylene glycol 400 and at pH 6. The activity and stability of enzyme was found to increase by addition of calcium chloride.

Energy-Cost Reduction in Starch Processing Using Aqueous Two Phase Reactor Systems

Saccharification is an energy intensive process of particular industrial interest in agribusiness. Considerable improvements to the energy costs of processing can be made by the elimination of multiple high temperature steps during liquefaction. To facilitate technology development for more energy efficient saccharification, the effectiveness of thermoseparating polymer-based aqueous two-phase reactor systems (ATPRS) in the enzymatic hydrolysis of starch was investigated. The partition behavior of pure α-amylase, and a recombinant, thermostable α-amylase (MJA1) from the hyperthermophile, Methanococcus jannaschii and amyloglucosidase in PEO-PPO/salt aqueous two-phase systems was evaluated. All of the studied enzymes partitioned unevenly in these systems. Hydrolysis of soluble starch and corn starch into glucose by thermostable α-amylase and amyloglucosidase was performed in an ATPRS coupled with temperature-induced phase separation. Use of the ATPRS reduced the hydrolysis time to half of that for single-phase processing, thus reducing energy inputs. The hydrolysis time was 18 hours for 20% soluble starch with an amyloglucosidase concentration of 2.18 unit mL−1 in the aqueous system, but only 11 hours in aqueous two-phase reactor system. The extent of product inhibition is greatly reduced. These results reveal the potential for polymer-enhanced extractive bioconversion of starch as a practical technology.

Cloning and characterization of a second alpha-amylase gene (LKA2) from Lipomyces kononenkoae IGC4052B and its expression in Saccharomyces cerevisiae.

Lipomyces kononenkoae secretes a battery of highly effective amylases (i.e. alpha-amylase, glucoamylase, isoamylase and cyclomaltodextrin glucanotransferase activities) and is therefore considered as one of the most efficient raw starch-degrading yeasts known. Previously, we have cloned and characterized genomic and cDNA copies of the LKA1 alpha-amylase gene from L. kononenkoae IGC4052B (CBS5608T) and expressed them in Saccharomyces cerevisiae and Schizosaccharomyces pombe. Here we report on the cloning and characterization of the genomic and cDNA copies of a second alpha-amylase gene (LKA2) from the same strain of L. kononenkoae. LKA2 was cloned initially as a 1663 bp cDNA harbouring an open reading frame (ORF) of 1496 nucleotides. Sequence analysis of LKA2 revealed that this ORF encodes a protein (Lka2p) of 499 amino acids, with a predicted molecular weight of 55,307 Da. The LKA2-encoded alpha-amylase showed significant homology to several bacterial cyclomaltodextrin glucanotransferases and also to the alpha-amylases of Aspergillus nidulans, Debaryomyces occidentalis, Saccharomycopsis fibuligera and Sz. pombe. When LKA2 was expressed under the control of the phosphoglycerate kinase gene promoter (PGK1(p)) in S. cerevisiae, it was found that the genomic copy contained a 55 bp intron that impaired the production of biologically active Lka2p in the heterologous host. In contrast to the genomic copy, the expression of the cDNA construct of PGK1p-LKA2 in S. cerevisiae resulted in the production of biologically active alpha-amylase. The LKA2-encoded alpha-amylase produced by S. cerevisiae exhibited a high specificity towards substrates containing alpha-1,4 glucosidic linkages. The optimum pH of Lka2p was found to be 3.5 and the optimum temperature was 60 degrees C. Besides LKA1, LKA2 is only the second L. kononenkoae gene ever cloned and expressed in S. cerevisiae. The cloning, characterization and co-expression of these two genes encoding these highly efficient alpha-amylases form an important part of an extensive research programme aimed at the development of amylolytic strains of S. cerevisiae for the efficient bioconversion of starch into commercially important commodities.

Kinetic enhancement of starch bioconversion in thermoseparating aqueous two-phase reactor systems

The extractive bioconversion of starch in an aqueous two-phase reactor system (ATPRS) was studied through experimentation and mathematical modeling. The phase-forming components included PEO-PPO-2500 (a random copolymer of ethylene oxide and propylene oxide with molecular weight of 2500) and MgSO 4. Partitioning of glucose and maltose in the PEO-PPO/MgSO 4 system was determined. Hydrolysis rates of soluble and corn starches in one-phase and aqueous two-phase reactor systems were compared. Starch consumption and glucose production kinetics were evaluated for α-amylase and amyloglucosidase separately as well as synergistically. A Michaelis–Menten kinetic model with product inhibition was employed to describe enzymatic hydrolysis. This model was expanded to include reaction with simultaneous partitioning for the two-phase system. Parametric studies of starch hydrolysis in the ATPRS with respect to the partition coefficient of the final hydrolysis product, glucose, were performed to simulate starch conversion profiles. The use of the ATPRS reduced the hydrolysis time to almost half of that for single-phase processing. These results were confirmed experimentally. The PEO-PPO-2500/MgSO 4 system enhanced the starch hydrolysis by decreasing the glucose inhibition. The hydrolysis reaction was completed in 10 h in ATPRS system while taking 18 h in one-phase aqueous system. The goodness of fit between model and experiments demonstrates that thermodynamic partition data, coupled with the lumped kinetic model for dual enzymatic hydrolysis and product inhibition are appropriate for describing the two-phase bioreactor system.

Bioconversion of starch into ethanol by a recombinant Saccharomyces cerevisiae strain YPG-AB

The direct fermentation of starch into ethanol by a recombinant Saccharomyces cerevisiae strain YPG/AB, which expresses Bacillus subtilis α-amylase and Aspergillus awamori glucoamylase as separately secreted polypeptides, was investigated in both batch and fed-batch fermenter systems under controlled conditions. A 34% increase was observed in ethanol production by YPG/AB in a 40 g l −1 initial starch containing medium supplemented with 4 g l −1 glucose. Ethanol productivities were calculated as 0.35, 0.33 and 0.27 g l −1 h −1 for media with pH 4.5, 5.6 and 6.5, respectively. Substrate controlled fed-batch cultures were used to increase the ethanol production rate. The amount of ethanol produced in fed-batch culture (47.5 g l −1) increased by 200% compared to batch culture (15.6 g l −1). Starch fermentation by S. cerevisiae YPG-AB strain was characterized by ethanol yields/productivities higher than those obtained in comparable fermentations on starch reported in literature.

Amylase partitioning and extractive bioconversion of starch using thermoseparating aqueous two-phase systems

The effectiveness of thermoseparating polymer-based aqueous two-phase systems (ATPS) in the enzymatic hydrolysis of starch was investigated. In this work, the phase diagrams of PEO–PPO-2500/ammonium sulfate and PEO–PPO-2500/magnesium sulfate systems were determined at 25 °C. The partition behavior of pure α-amylase and amyloglucosidase in four ATPS, namely, PEO–PPO/(NH 4) 2SO 4, PEO–PPO/MgSO 4, polyethylene glycol (PEG)/(NH 4) 2SO 4, and PEG/MgSO 4, was evaluated. The effects of phase-forming component concentrations on the enzyme activity and partitioning were assessed. Partitioning of a recombinant, thermostable α-amylase (MJA1) from the hyperthermophile, Methanococcus jannaschii was also investigated. All of the studied enzymes partitioned unevenly in these polymer/salt systems. The PEO–PPO-2500/MgSO 4 system was extremely attractive for starch hydrolysis. Polymer-based starch hydrolysis experiments containing PEO–PPO-2500/MgSO 4 indicated that the use of ATPS had a significant effect on soluble starch hydrolysis. Batch starch hydrolysis experiments with PEO–PPO/salt two-phase systems resulted in higher production of maltose or glucose and exhibited remarkably faster hydrolysis. A 22% gain in maltose yield was obtained as a result of the increased productivity. This work is the first reported application of thermoseparating polymer ATPS in the processing of starches. These results reveal the potential for thermoseparating polymer-enhanced extractive bioconversion of starch as a practical technology.

Bioconversion of starch to ethanol in a single-step process by coculture of amylolytic yeasts and Saccharomyces cerevisiae 21

Ethanol production by a coculture of Saccharomyces diastaticus and Saccharomyces cerevisiae 21 was 24.8 g/l using raw unhydrolysed starch in a single-step fermentation. This was 48% higher than the yield obtained with the monoculture of S. diastaticus (16.8 g/l). The maximum ethanol fermentation efficiency was achieved (93% of the theoretical value) using 60 g/l starch concentration. In another coculture fermentation with E. capsularis and S. cerevisiae 21, maximum ethanol yield was 16.0 g/l, higher than the yield with the monoculture of Endomycopsis capsularis. In batch fermentations using cocultures maximum ethanol production occurred in 48 h of fermentation at 30°C using 60 g/l starch. Fermentation efficiency was found lower in a two-step process using α-amylase and glucoamylase-treated starch.

Conversion of Liquified Starch into Glucose Using a Novel Glucoamylase System

AbstractThe production of sweeteners from starch by enzymes has been commercially successful for many years. However, the real need for improving the current industrial processes for bioconversion of starch, which is chiefly obtained from the wet milling of corn, into the monosaccharides glucose and fructose still exists. Currently, most starch processing in the corn wet milling industry is achieved by using the enzymes α‐amylase, amyloglucosidase and glucose isomerase. This lecture deals with the production of glucose from dextrins by means of amyloglucosidase systems. The amyloglucosidase preparations commonly applied in industry are mixtures containing various enzymes. The maximum obtainable conversion of dextrins into glucose is determined by the thermodynamic and kinetic behaviour of the enzymes present in the amyloglucosidase mixtures. Therefore, knowledge of the composition and properties of the enzymes may lead to the decision to alter the composition of the enzyme system as a possible means of improving the glucose production process. In the search for various amylolytic components advanced chromatography techniques were applied and the enzymes found were used in saccharification studies.