Initial Starch Concentration Research Articles

Upcycling of industrial pea starch by rapid spray nanoprecipitation to develop plant-derived oil encapsulated starch nanoparticles for potential agricultural applications

Starch is one of the natural encapsulant materials widely used in food, pharmaceutical and cosmetic industries. Starch with high amylose content (above 40 %, w/w) is prone to form single helices V-type allomorph with a hydrophilic outer surface and a hydrophobic inner cavity making them suitable for encapsulation of hydrophobic compounds such as essential oils, fatty acids, and vitamins. Pea starch obtained from pea protein processing industries have a high amylose content (40 %, w/w) rendering them unsuitable for direct food applications as ingredients. Therefore, in this study, an in-house spraying procedure was used to synthesize nanoparticles using pea starch, to encapsulate neem oil, a natural antimicrobial compound obtained from neem plant (Azadirachta indica) seed. The synthesis of the oil-encapsulated starch nanoparticles (OESNP) was optimized using a Box-Behnken experimental design to study the influence of the processing parameters such as the initial starch concentration, homogenization speed, duration of homogenization, sample injection rate, and quantity of antisolvent (ethanol). The optimized sample showed an 80–90 % encapsulation efficiency and particle size of <500 nm. The spherical OESNPs also demonstrated sustained release of the oil compared to free oil when dispersed in water. X-ray diffraction analysis revealed the coexistence of C-type and V-type polymorphs in the loaded and unloaded nanoparticles. It is concluded that the synthesized OESNPs with controlled release hold the potential to utilize industrial pea starch waste for the delivery of natural pesticides in agriculture.

Kinetic modeling of advanced starch oxidation with ozone in basic solutions

ABSTRACT The growing use of ozone (O3) in the last years to clean and enhance the physicochemical properties of starches, widely used as additives in food, beverage, and pharmaceutical industries, calls for a better understanding of their oxidation process. High pH, however, decomposes O3 rapidly, forming highly-oxidant radicals, thus increasing the complexity of the reaction system. In this study, a kinetic model for the ozonation reaction of starch in an alkaline medium was developed and experimentally validated. Firstly, the concentration of hydroxyl radicals (●OH) over the reaction time is evaluated through the degradation of pCBA (a probe compound) to later evaluate and model the oxidation process of starch based on Chemical Oxygen Demand (COD) measurements. By using a semi-batch reactor containing alkaline solutions at pH = 13, different O3 concentrations (0–42.30 g/Nm3) and temperatures (20–60 °C), a pseudo first-order kinetic model was proposed to model the pCBA-ozone reaction. This model estimates the ●OH formation, being [●OH] constant and proportional to the O3 continuous dose. Therefore, under the conditions studied, ●OH is a non-limiting reactant independent of temperature. The activation energy was estimated at 14.2 ± 2.1 and 14.5 ± 0.6 KJ/mol for 21.15 and 42.30 gO3/Nm3, respectively. Then, COD data were used to propose a kinetic model for ozone-starch oxidation in alkaline media, where besides O3 concentration and temperature, starch concentration (600–1700 mg/L) was also varied. According to the results, higher temperatures and longer reaction times resulted in a greater COD reduction, being it more pronounced at lower initial starch concentration. The activation energy of the ozone radicals-starch reaction was estimated at 8.1 ± 0.4 KJ/mol, being significantly lower than those reported for the reaction between pCBA and ●OH.

Dextrose Equivalent Analysis of Acid Hydrolysed Corn and Cassava Starch Sourced from Ghana

The use of acid hydrolysis to convert starch into dextrose can be difficult and time-consuming. The process requires high acidic medium and temperature which tends to contaminate the end-product hydrolysate. Therefore, this research was carried out to obtain optimum conditions necessary to produce a high and quality Dextrose Equivalent by varying the initial starch concentration and acid volume. The mass of corn and cassava starch and the total hydrochloric acid volume used for the hydrolysis ranged from 100 to 400 g and 1-3 liters respectively. The results showed that the optimum conditions for hydrolyzing the two starch types to Dextrose were within a temperature range of 100°C-120°C, 12 w/w% starch concentration, 4 atmospheric pressure and 30 minutes operating time. The optimum conditions produced a Dextrose Equivalent of 79.80% and 78.66% for cassava and corn starch respectively. The amount of dextrose produced in the process is a function of temperature, pressure, acid volume, operating time and initial starch concentration. Experimental results also confirmed an increase in pH of the hydrolysate with a temperature rise, and this influenced the Dextrose quality. The outcomes provided new findings to complement existing outcomes on how initial starch concentration and acid volume affect Dextrose Equivalent by acid-type hydrolysis.

English

The performance of a hybrid of Saccharomyces cerevisiae and Saccharomyces paradoxus (Yeast B) compared with an industrial strain of S. cerevisiae (Yeast A) was studied. The two strains of yeasts: Yeast A obtained from the Bioresources Development Centre, National Biotechnology Development Agency Ogbomosho and Yeast B obtained from Scotch Whisky Research Laboratory in Edinburgh, Scotland (Strain 63M) were studied using the SLSF method for bioethanol production at various initial starch concentrations (20, 30 and 50%). The cassava starch used was extracted from Tropical Manihot esculenta (TME 419) cassava strain while the SLSF method for bioethanol production was initiated by adding granular starch hydrolysing enzyme with the yeast strains into the starch solutions at room temperature. The results obtained showed that Yeast B has higher bioethanol yield and tolerance generating 70.34, 87.34 and 120.53 ml/L compared to the Yeast A which produced 63.4, 72.73 and 112.6 ml/L at 20, 30 and 50% starch concentrations respectively. The study suggests that the hybrid strain of S. cerevisiae and S. paradoxus out performs the industrial strain and can favorably substitute or displace the industrial strains for bioethanol production. Key words: Bioethanol, cassava, fermentation, hybrid, simultaneous liquefaction saccharification and fermentation (SLSF), yeast, Saccharomyces cerevisiae, Saccharomyces paradoxus.

A new kinetic model for growth based on simultaneous substrate and biomass limitation in solid-state fermentation using agar spheres as the model substrate

Substrate limitation is a major concern in solid-state fermentation, especially for bacteria, as they are not capable of penetrating into the substrate particles. The use of a model substrate, such as agar spheres, makes it possible to study the intra-particle transfer phenomena in solid-state fermentation, reduce the system complexity, and determine the cell dry weight (CDW). A semi-mechanistic model was used to predict the growth of Pseudomonas aeruginosa on agar spheres that contain starch as the only carbon source. The model was developed by introducing a new simultaneous substrate- and biomass-limited growth kinetic equation. The parameters of the growth kinetic were estimated by fitting the experimental data of both the CDW and cumulative CO2 production on agar spheres containing glucose. Statistical analysis (F-test) showed that the new growth kinetic equation was significantly better than the conventional substrate-limited growth kinetics. The model predictions were validated by the experimental data of growth, starch concentration and cumulative CO2 production (CCP) of Pseudomonas aeruginosa growing on agar spheres containing starch in aerated small packed-bed bioreactors. The model confirmed that at high initial starch concentration, free glucose and O2 were not the limiting factors, and bacterial growth is limited by other factors that are related to the amount of biomass in the biofilm.

Enhanced production of exopolysaccharides using industrial grade starch as sole carbon source

Industrial grade soluble corn starch was used directly and effectively as the fermentation substrate for microbial exopolysaccharides production. Bacillus subtilis mutant strain NJ308 grew with untreated starch raw material as the sole carbon source. The real-time PCR results demonstrated that up-regulated genes encoding N-acetylglucosaminyltransferase, mannosyltransferase, and N-acetylglucosamine-1-phosphate uridyltransferase were the key elements of B. subtilis mutant strain NJ308 for exopolysaccharides production from industrial grade starch. Subsequently, the culture conditions for B. subtilis NJ308 were optimized using Plackett-Burman design and central composite design methods, and the related key genes in the synthesis pathway of exopolysaccharides from the starch raw material were analyzed by real-time PCR. The maximum exopolysaccharides titration (3.41g/L) was obtained when the initial starch concentration was 45g/L. This corresponds to volumetric productivity values of 71.04mg/Lh.

Pickering emulsions stabilized by media-milled starch particles

A simple, organic solvent-free media-milling process was applied to modify the structure and morphology of maize starch granules. During the milling process, the sizes of starch granules reduced dramatically while their crystalline structure was largely damaged as verified by differential scanning calorimetry and X-ray diffraction. The surface hydrophobicity of milled starch was also characterized by contact angle measurement. These media-milled starch suspensions with different starch concentrations (i.e., 2.4%, 7.2% and 10.0%) were used as stabilizers to form Pickering emulsions. The droplet sizes of the Pickering emulsions prepared in this study ranged from approximately 10μm to 900μm depending on the milling time and the initial starch concentration. The droplet sizes decreased with prolonged milling time and increased initial starch concentration. Milled starch particles of around 100nm anchored at the emulsion interfaces were observed by cryo-scanning electron microscopy. Although some emulsions creamed immediately after homogenization, most emulsions exhibited stability against coalescence during the long-term storage of 6months. The emulsions also exhibited benign stability against a wide range of pH, ionic strength and temperature conditions. This research provides a new green approach to form food-grade emulsions to deliver active food ingredients.

Cassava roots: perspectives of a traditional staple for bio-solvents production

Sidi Seibou T.M., Rychtera M., Melzoch K. (2015): Cassava roots: perspectives of a traditional staple for Clostridium acetobutylicum DSM 1731. The purpose of these tests was to determine the initial starch concentration which could be used as a starting point for the fermentation in laboratory bioreactors. In this case, we used two culture media: the first one made with cassava starch (M1), and the second one with mashed fresh cassava (M2). The culture media were supplemented with organic and inorganic nutrients. Fermentation in M1 medium resulted in the production of 17.8 g/l solvents, i.e. 12.3 g/l butanol, 3.7 g/l acetone, and 1.8 g/l ethanol, while in M2 it provided 16.2 g/l solvents representing approximately 11.4 g/l of butanol, 3.0 g/l of acetone, and 1.8 g/l of ethanol. The optimum production of butanol in M1 was 12.3 g/l in 96 h of fermentation, which is a low yield of 25% and 0.13 g/l/h productivity. Although the fermentation in medium M2 was also low (with 11.4 g/l butanol optimally), it allowed to save on the nutrient sup -

Experimental studies and kinetic modeling of cyclodextrin glucanotransferase production from starch with the use ofBacillussp. DSM 2523

Cyclodextrin glucanotransferase (CGTase) production from starch with the use of Bacillus sp. DSM 2523 was studied. The specific growth rate (µ) considering the initial starch concentrations (S0) ranging from 0.2% to 2% w/v, was determined and a maximum value for µ of 0.1151/h was found at S0 = 0.5% w/v. The maximum specific CGTase production rate (qP) at S0 = 0.2% w/v, was 1.1105/h with considerable fluctuations in enzyme production. By performing a repeated batch experiment using dextrin as feeding substrate, the cell's ability to maintain its responses for an extended period of time was examined. The trend toward a decrease in the µ value and qP with an increase in the substrate concentration was evident. The experimental data showing the inhibitory function of starch on the growth and enzyme production were best predicted using Haldane model. On basis of the cell maintenance concept the observed dependency of the growth yield (Y) on the starch concentration was applied and the relationship between maintenance energy and µ was evaluated. At concentrations of starch below 0.5% w/v, the constant maintenance energy can be obtained. The variation of maintenance energy dependency on µ was assessed in the inhibited culture system (S0 ≥ 0.5% w/v).

Preparation of water‐soluble oxidized starch with high carbonyl content by sodium hypochlorite

Water‐soluble oxidized starch with high carbonyl content (DOCO = 0.40) was prepared using a one‐step method with sodium hypochlorite (NaClO) as the primary oxidant and under the mediation of sodium bromide (NaBr) and hydroxylamine hydrochloride (NH2OH · HCl). The influences of pH, initial starch concentration, and the amount of NaBr and NH2OH · HCl on the carbonyl and carboxyl content were discussed. The molar ratio of carbonyl to carboxyl groups can be adjusted from 0.8 to 2.2 by controlling the dropping speed of NaClO. The formation of carbonyl and carboxyl groups on the oxidized starch was confirmed by Fourier‐transform infrared (FT‐IR) and 13C NMR spectroscopy. The molecular weight of the oxidized starch determined by SEC revealed modest degradation. Besides, a good solubility of the oxidized starch in cold water was also proved based on the study of its solubility and swelling properties.

Interaction of cationic starch derivatives and cellulose fibres in the wet end and its correlation to paper strength with a statistical evaluation

AbstractThe adsorption onto a softwood pulp of cationic modified starches with a degree of substitution (DS) ranging from 0.015 to 0.130 and native potato starch was investigated using a method based on size exclusion chromatography‐multi angle laser light scattering (SEC‐MALLS). This technique provides information about the amount and molecular composition of the adsorbed starch product such as the AP–AM‐ratio, the average MW and molar mass distribution. Factors influencing adsorption, like the electrolyte content in the suspension and the initial starch polysaccharide concentration, were investigated. Furthermore, hand sheets were made and the resulting mechanical paper strength was tested. Results were analysed statistically using analysis of variance. Representative results were discussed in detail. In general, low‐substituted cationic starch (DS 0.030) exhibited a higher degree of adsorption and resulted in high paper strength when there was a low electrolyte content in the starch–pulp‐suspension. However, high amounts of electrolytes impeded electrostatic interaction of the charged groups of the starch polysaccharides and cellulose fibre due to partial screening and therefore strongly limited adsorption. This resulted in lowered mechanical paper strength. The water quality of the suspensions had little impact on the polyelectrolyte adsorption of the highly substituted cationic starch (DS 0.100). However, paper strength was markedly higher in the case of starch adsorption where there was a high ionic content and when both starch polysaccharides–AP and AM– were adsorbed. The initial starch concentration determined starch adsorption both quantitatively and qualitatively and subsequently paper strength as well. The relation between adsorption behaviour and paper strength was discussed, particularly in the case of 6% initial starch concentration. In deionised water (DW), the low‐substituted starch (DS 0.03) adsorbed onto the pulp to a greater extent with an AP–AM‐ratio similar to that of the initial starch. Moreover, this achieved the best strength properties in contrast to 36 dGH, where less starch adsorbed and that being almost exclusively AP. In water with 36 dGH, the highly substituted starch (DS 0.100) with both the AP and AM was absorbed and this resulted in higher paper strength. In contrast, AM was almost exclusively adsorbed in DW. Increasing the initial starch concentration increased the amount adsorbed while subsequently changing the AP–AM‐ratio towards increased AM adsorption and decreased AP adsorption in the case of DS 0.100 in DW. Exclusive adsorption of AM markedly lowered the development of the paper strength.

Biohydrogen production from sago starch in wastewater using an enriched thermophilic mixed culture from hot spring

We investigated the feasibility of producing biohydrogen from sago starch in wastewater using a thermophilic mixed culture enriched from a hot spring in southern Thailand (PGK). The effects of repeated batch cultivations, the dependence of the initial pH values ranging from 5.0 to 8.0 and the initial sago starch concentrations ranging from 2.5 to 60 g/l as well as the utilization of 4 different starch types (gelatinized dry starch, non-gelatinized dry starch, gelatinized wet starch, and non-gelatinized wet starch) were examined in batch experiments at 60 °C. Microbial community structures were also investigated. The methane-free biogas evolved contained up to 55% hydrogen, with the remainder comprising carbon dioxide. Repeated batch cultivation under identical conditions improved the hydrogen yield. Gelatinized dry starch at an initial pH of 6.5 and an initial starch concentration of 2.5 g/l gave the maximum hydrogen yield of 422 ml-H 2/g-starchadded (80% of the theoretical limit). PCR-DGGE profiles of 16S rRNA gene fragments from the cultures showed that the predominant hydrogen producers were closely related to thermophilic anaerobic bacteria, including Thermoanaerobacterium saccharolyticum, Thermoanaerobacterium thermosulfurigenes, and uncultured Thermoanaerobacterium sp., all of which probably produced hydrogen with simultaneous generation of ethanol. The thermophilic bacilli capable of utilizing starch, including Bacillus sp., Anoxybacillus sp., Bacillus lentus, and Geobacillus sp., were also found in the starch cultures, but mainly in the non-gelatinized wet starch culture.

Lactic acid production directly from starch in a starch-controlled fed-batch operation using Lactobacillus amylophilus

Based on the batch results, we constructed a simplified simultaneous saccharification and fermentation (SSF) model for the simulation of lactic acid production directly from unhydrolyzed potato starch using Lactobacillus amylophilus. The results of batch operation at different initial starch concentrations (20, 40 and 60g/l) indicated that a higher initial starch concentration would lead to a slightly lower productivity, but would largely decrease the yield. Among that, the batch with 20g/l of initial starch had the maximum productivity and the maximum yield, which would be 0.31g/(lh) and 98% (g/g), respectively. In view of increasing the productivity and the final lactic acid concentration, a starch-controlled fed-batch operation with 20g/l of initial starch was performed. It showed the fed-batch operation with starch controlled at 8±1g/l by adjusting the starch-feeding rate led to the maximum productivity of 0.75g/(lh) and the yield of 69%.

Kinetic and Optimization Studies on Ethanol Production from Corn Flour

Studies on Simultaneous Saccharification and Fermentation (SSF) of corn flour, a major agricultural product as the substrate using starch digesting glucoamylase enzyme derived from Aspergillus niger and non starch digesting and sugar fermenting Saccharomyces cerevisiae in a batch fermentation. Experiments based on Central Composite Design (CCD) were conducted to study the effect of substrate concentration, pH, temperature, enzyme concentration on Ethanol Concentration and the above parameters were optimized using Response Surface Methodology (RSM). The optimum values of substrate concentration, pH, temperature and enzyme concentration were found to be 160 g/l, 5.5, 30°C and 50 IU respectively. The effect of inoculums age on ethanol concentration was also investigated. The corn flour solution equivalent to 16% initial starch concentration gave the highest ethanol concentration of 63.04 g/l after 48 h of fermentation at optimum conditions of pH and temperature. Monod model and Logistic model were used for growth kinetics and Leudeking - Piret model was used for product formation kinetics.

Simultaneous saccharification and fermentation of wheat bran flour into ethanol using coculture of amylotic Aspergillus niger and thermotolerant Kluyveromyces marxianus

Studies on simultaneous saccharification and fermentation (SSF) of wheat bran flour, a grain milling residue as the substrate using coculture method were carried out with strains of starch digesting Aspergillus niger and nonstarch digesting and sugar fermenting Kluyveromyces marxianus in batch fermentation. Experiments based on central composite design (CCD) were conducted to maximize the glucose yield and to study the effects of substrate concentration, pH, temperature, and enzyme concentration on percentage conversion of wheat bran flour starch to glucose by treatment with fungal α-amylase and the above parameters were optimized using response surface methodology (RSM). The optimum values of substrate concentration, pH, temperature, and enzyme concentration were found to be 200 g/L, 5.5, 65°C and 7.5 IU, respectively, in the starch saccharification step. The effects of pH, temperature and substrate concentration on ethanol concentration, biomass and reducing sugar concentration were also investigated. The optimum temperature and pH were found to be 30°C and 5.5, respectively. The wheat bran flour solution equivalent to 6% (w/V) initial starch concentration gave the highest ethanol concentration of 23.1 g/L after 48 h of fermentation at optimum conditions of pH and temperature. The growth kinetics was modeled using Monod model and Logistic model and product formation kinetics using Leudeking-Piret model. Simultaneous saccharificiation and fermentation of liquefied wheat bran starch to bioethanol was studied using coculture of amylolytic fungus A. niger and nonamylolytic sugar fermenting K. marxianus.

Analysis of the continuous phase of the modified waxy maize starch suspension

The continuous phase of the suspension of swollen-in-water modified waxy maize starch was analysed. The composition, concentration and molecular weight of the substance released from modified starch granules were determined. Starch granules were swollen in excess water at 73 °C and held at this temperature for 1 min. Centrifugation was used to separate the granules from the supernatant; the latter was then submitted to physico-chemical analysis. Surface tension measurements showed that the supernatant was different from pure water indicating the presence of dissolved polymeric material(s). Differential Scanning Calorimetry and iodine staining results revealed the presence of amylopectin. Analytical Ultracentrifugation and Size Exclusion Chromatography coupled with a Multi-angle Laser Light Scattering were used to determine the sedimentation coefficient and weight–average molecular weight of the soluble amylopectin fraction as well as giving an indication of solution concentration. The molecular weight of dissolved amylopectin was around 1.5 × 10 6 g/mol and its concentration in the supernatant varied from 0.6 to 6.7 mg/mL for initial 10 mg/mL and 50 mg/mL starch suspensions, respectively. The sedimentation coefficient, weight–average molecular weight and amylopectin concentration in the supernatant all increased non-linearly with the initial starch concentration in the suspension.

Modeling and experimental studies on intermittent starch feeding and citrate addition in simultaneous saccharification and fermentation of starch to flavor compounds

Simultaneous saccharification and fermentation (SSF) is a combined process of saccharification of a renewable bioresource and fermentation process to produce products, such as lactic acid and ethanol. Recently, SSF has been extensively used to convert various sources of cellulose and starch into fermentative products. Here, we present a study on production of buttery flavors, namely diacetyl and acetoin, by growing Lactobacillus rhamnosus on a starch medium containing the enzyme glucoamylase. We further develop a structured kinetics for the SSF process, which includes enzyme and growth kinetics. The model was used to simulate the effect of pH and temperature on the SSF process so as to obtain optimum operating conditions. The model was experimentally verified by conducting SSF using an initial starch concentration of 100 g/L. The study demonstrated that the developed kinetic was able to suggest strategies for improved productivities. The developed model was able to accurately predict the enhanced productivity of flavors in a three stage process with intermittent addition of starch. Experimental and simulations demonstrated that citrate addition can also lead to enhanced productivity of flavors. The developed optimal model for SSF was able to capture the dynamics of SSF in batch mode as well as in a three stage process. The structured kinetics was also able to quantify the effect of multiple substrates present in the medium. The study demonstrated that structured kinetic models can be used in the future for design and optimization of SSF as a batch or a fed-batch process.

Fermentative production of L(+)‐lactic acid from starch hydrolyzate and corn steep liquor as inexpensive nutrients by batch culture of Enterococcus faecalis RKY1

AbstractBACKGROUND: Attempts were made to determine the lactic acid production efficiency of novel isolate, Enterococcus faecalis RKY1 using four different starches (corn, tapioca, potato, and wheat starch) with different concentrations (50, 75, 100, and 125 g L−1) and corn steep liquor as an inexpensive nitrogen source.RESULTS: The yield of lactic acid from each starch was higher than 95% based on initial starch concentrations. High lactic acid concentration (129.9 g L−1) and yield (1.04 g‐lactic acid g−1‐starch) were achieved faster (84 h) from 125 g L−1 of corn starch. Among the starches used, tapioca starch fermentation usually completed in a shorter incubation period. The final dry cell weight was highest (7.0 g L−1) for the medium containing 75 g L−1 of corn starch, which resulted in maximum volumetric productivity of lactic acid (3.6 g L−1 h−1). The addition of 30 g L−1 corn steep liquor supplemented with a minimal amount of yeast extract supported both cell growth and lactic acid fermentation.CONCLUSION: Enterococcus faecalis RKY1 was found to be capable of growing well on inexpensive nutrients and producing maximum lactic acid from starches and corn steep liquor as lower‐cost raw materials than conventionally‐used refined sugars such as glucose, and yeast extract as an organic nitrogen source in laboratory‐scale studies. These fermentation characteristics are prerequisites for the industrial scale production of lactic acid. Copyright © 2008 Society of Chemical Industry

Gentamicin production by Micromonospora echinospora (Me‐ 22) in stirred tank reactor: effect of various parameters

Effect of production medium components, initial starch and soyabean meal concentrations, for the enhanced production of gentamicin by Micromonospora echinospora (Me- 22) was studied in a lab scale stirred tank reactor. Also effect of different aeration (0.5, 1, 2, and 4 vvm) and agitation rates (100, 200, 300 and 400 rpm) in a stirred tank reactor was examined. A maximum gentamicin concentration of 2.68 g l(-1) was achieved in the medium having low concentrations of initial starch (7.5 g l(-1)) and high concentrations of initial soyabean meal (4 g l(-1)). Both aeration and agitation significantly affected gentamicin concentration, productivity and biomass formation. The maximum gentamicin concentration of 4.12 g l(-1) and the highest yield of gentamicin on substrate 0.967 g g(-1) were obtained at impeller speed of 200 rpm and aeration rate of 2 vvm. Under optimal culture conditions in STR the production of gentamicin could be increased 3 fold when compared with shake flask.

Exploring optimal environmental factors for fermentative hydrogen production from starch using mixed anaerobic microflora

Our previous work demonstrated that an acclimated mixed bacterial consortium was able to produce H 2 from sugar substrates. To reduce the medium cost for more commercially viable H 2 production, cassava starch was used as the feedstock to produce H 2 via dark fermentation. Three factors, namely, temperature, pH and starch concentration ( C starch ) , were intensively examined for their effects on H 2 production activity. The H 2 production kinetics was determined using a Monod-type kinetic model. The results show that mesophilic temperature ( 37 ∘ C ) is preferable for H 2 production with the H 2 -producing sludge used. The H 2 production efficiency and the composition of soluble metabolites were found to be highly sensitive to the change in pH, as pH 6.0 seemed to give the best overall H 2 production performance. In a non-pH-controlled culture (initial pH = 8.5 ), ethanol and butyrate were the major soluble metabolites, whereas the predominant metabolites switched to butyrate alone (accounting for 70–80% of total soluble microbial products) when the culture pH was controlled at a fixed level ranging from 5.5 to 7.0. Meanwhile, the maximum H 2 production rate occurred when the initial starch concentration was 24 g COD/l. The dependence of H 2 production rate on starch concentration could be described by using Monod-type model and the predicted kinetic constants, namely, maximum H 2 production rate ( v max , H 2 ) and Monod constant ( K s ) , were 1741 ml/h/l and 16.28 g COD/l, respectively. Under the optimal conditions ( 37 ∘ C , pH 6.0, C starch = 24 g COD / l ), the H 2 production rate increased to 1119 ml/h/l, while a high H 2 yield of 9.47 mmol H 2 /g starch was obtained. This performance appeared to be superior to that obtained from other starch-to-bio H 2 systems reported in the literature.