Production of detoxified sorghum straw hydrolysates for fermentative purposes

Sorghum straw can be hydrolysed to obtain monosaccharide solutions, mainly containing xylose. The usual biotechnological application of xylose is its bioconversion to xylitol. The global process from straw to xylitol can give an added value to the sorghum straw. The process has the following sequential steps: reduction of size, acid hydrolysis, neutralization, detoxification, fermentation, recovery and purification. This work deals with the optimization of the detoxification process of sorghum straw hydrolysates with activated charcoal. The variables evaluated were pH (1–5), contact time (20–60 min) and activated charcoal charge (20–33 g kg^?1). Mathematical models were obtained through a factorial experimental design. The models suggest that optimal conditions for detoxification are pH 1, contact time of 29 min and a charcoal charge of 33 g kg^?1. These conditions allowed hydrolysates with 54.2 g xylose L^?1, 13.5 g glucose L^?1, 12 g arabinose L^?1, 0.2 g furfural L^?1 and 0.0 g acetic acid L^?1 to be obtained. The results suggest that performing the detoxification step before the neutralization step gave the best outcome. Fermentations by Candida parapsilosis NRRL Y‐2315 were performed and it was confirmed that the treated hydrolysate is suitable for xylitol production, yielding up to 17 g L^?1 of this polyol. Copyright © 2006 Society of Chemical Industry     

Production of fermentable media from vine‐trimming wastes and bioconversion into lactic acid by Lactobacillus pentosus

Trimmings of vineshoots, an agricultural waste with little use, were hydrolysed with dilute sulphuric acid (1–5%) in order to obtain sugar solutions suitable as fermentation media. The operational conditions for hydrolysis were selected on the basis of both the generation of hemicellulosic sugars (mainly xylose) and glucose and the concentrations of reaction byproducts affecting fermentation (furfural, hydroxymethylfurfural and acetic acid). Hemicellulosic hydrolysates were supplemented with nutrients and fermented with Lactobacillus pentosus, without any previous detoxification stage, to produce lactic acid. Under the best operational conditions assayed (3% H₂SO₄ and 15 min), 21.8 g lactic acid l^?1 was produced (Q_P = 0.844 g l^?1 h^?1, Y_P/S = 0.77 g g^?1), which represents a theoretical yield of 99.6%. Acetic acid was the primary byproduct formed from xylose, at about 25% of the lactic acid level. Copyright © 2004 Society of Chemical Industry     

Xylitol bioproduction from wheat straw: hemicellulose hydrolysis and hydrolyzate fermentation

A 2² central composite design with five center points was performed to estimate the effects of temperature (120, 130 and 140 °C) and acid loading (100, 150 and 200 mg g^?1) on the yield of monomeric xylose recovery from wheat straw hemicellulose (Y_S/RM). Under the best hydrolysis condition (140 °C and 200 mg g^?1), a Y_S/RM of 0.26 g g^?1 was achieved. After vacuum concentration and detoxification by pH alteration and active charcoal adsorption, the hydrolyzate was used as source of xylose for xylitol bioproduction in a stirred tank reactor. A xylitol production of 30.8 g L^?1 was achieved after 54 h^?1 of fermentation, resulting in a productivity (Q_P) of 0.57 g L^?1 h^?1 and bioconversion yield (Y_P/S) of 0.88 g g^?1. The maximum specific rates of xylose consumption and xylitol production were 0.19 and 0.15 g g^?1 h^?1, respectively. Copyright © 2006 Society of Chemical Industry     

Determination of Quercetin, Gallic Acid, Resveratrol, Catechin and Malvidin in Brazilian Wines Elaborated in the Vale do São Francisco Using Liquid–Liquid Extraction Assisted by Ultrasound and GC-MS

In this work, a fast and simple methodology has been applied for the determination of gallic acid, resveratrol, catechin and malvidin in Brazilian wines by gas chromatography–mass spectrometry. The procedure included a stage of ultrasound-assisted liquid–liquid extraction and subsequent derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and GC-MS analysis. The limit of detection varied from 0.41 to 1.18 mg?L^?1 in all the analytes. The relative standard deviations calculated for 8.0 and 20 mg?L^?1 were 1.90 and 0.82 % for gallic acid, 3.08 and 1.22 % for catechin, 1.30 and 0.44 % for malvidin, 1.50 and 0.53 % for resveratrol, and 1.41 and 0.61 % for quercetin. The developed methodology was applied for the analysis of red wine samples collected in the São Francisco region, Bahia state, Brazil. Quercetin concentration varied from 2.4 to 3.0 mg?L^?1, gallic acid 21.4–56.3 mg?L^?1, resveratrol 1.5–5.9 mg?L^?1, malvidin 15.3–32.2 mg?L^?1, and catechin 11.71–18.2 mg?L^?1. The obtained concentrations are in agreement with those reported in the literature.     

Simultaneous lactic acid and xylitol production from vine trimming wastes

Hemicellulosic hydrolyzates from vineshoot trimmings obtained by dilute sulfuric acid hydrolysis were evaluated for xylitol production by Debaryomyces hansenii NRRL Y‐7426. Bioconversion was not efficient, however, since a mixture of products (mainly ethanol) was achieved. Taking into account that hexoses (such as glucose or mannose) can inhibit xylose metabolism by repression and inactivation of the xylose transport system or catabolic enzymes and that these hemicellulosic hydrolyzates are characterized by a high glucose concentration, a novel technology was developed, sequentially transforming glucose into lactic acid by Lactobacillus rhamnosus followed by fermentation of xylose into xylitol by Debaryomyces hansenii after L. rhamnosus removal by microfiltration. Optimal conditions were achieved using detoxified concentrated hemicellulosic hydrolyzates, after CaCO₃ addition in both stages of fermentation and using nitrogen purges after sampling in order to reduce the oxygen dissolved. Under these conditions 31.5 g lactic acid L^?1 (Q_LA = 1.312 g L^?1 h^?1 and Y_LA/S = 0.93 g g^?1) and 27.5 g xylitol L^?1 (Q_Xylitol = 0.458 g L^?1 h^?1 and Y_Xylitol/S = 0.53 g g^?1) were produced. Finally, lactic acid was selectively recovered using the resin Amberlite IRA 400 (0.0374 g of lactic acid g^?1 of dry resin), allowing a further recovery of xylitol by sequential stages of adsorption, concentration, ethanol precipitation, concentration and crystallization to obtain food‐grade xylitol according to a developed process. Copyright © 2007 Society of Chemical Industry     

Multi-Residue Determination of Pesticides in Açai Tropical Fruit (Euterpe oleracea) by Matrix Solid-Phase Dispersion Combined with Liquid Chromatography

An extraction method based on matrix solid phase dispersion was developed to determine bromuconazole, fenbuconazole, parathion-methyl, kresoxim-methyl, and teflubenzuron in açai using liquid chromatography with ultraviolet diode array detector. The best results were obtained using 1.0 g of açai, 3.0 g of neutral alumina as the dispersant sorbent, and cyclohexane/ethyl acetate (1:1, v/v, 20 mL) as an eluting solvent. The method was validated using açai samples fortified with pesticides at three concentration levels (0.25, 0.5, and 1.0 mg kg^?1). Average recoveries (seven replicates) ranged from 66 to 119 %, with relative standard deviations between 1.4 and 20 %. The detection and quantification limits for açai ranged from 0.02 to 0.05 mg kg^?1 and from 0.05 to 0.1 mg kg^?1, respectively.     

Modelling of the hydrolysis of sorghum straw at atmospheric pressure

Sorghum straw is a renewable, cheap and widespread resource. The acid hydrolysis of sorghum straw to obtain xylose solutions could be a good alternative for this abundant resource. The H₂SO₄ hydrolysis of sorghum straw at two different temperatures (80 and 100 °C) and three H₂SO₄ concentrations (2, 4 and 6%) using a solid/liquid ratio of 1:10 (w/w) was studied. Kinetic parameters of mathematical models for predicting the concentrations of xylose, glucose, acetic acid and furfural were determined. The activation energy of the release reaction was 183.3 kJ mol^?1 for xylose and 185.8 kJ mol^?1 for glucose. The optimal conditions found were 6% H₂SO₄ at 100 °C for 60 min, which allow one to obtain a solution with 18.27 g xylose l^?1, 6.78 g glucose l^?1, 0.7 g furfural l^?1 and 1.35 g acetic acid l^?1. It is concluded that this process has potential for utilisation of this renewable lignocellulosic resource. © 2002 Society of Chemical Industry     

Effect of glycerol and dihydroxyacetone concentrations in the culture medium on the growth of acetic acid bacteria Gluconobacter oxydans ATCC 621

Bacteria of the species Gluconobacter oxydans are applied in the industrial production of dihydroxyacetone (DHA) via glycerol oxidation. The major problem of this biotransformation involves process inhibition by substrate and/or product. Improper initial concentration of glycerol and increasing DHA concentration may inhibit the metabolic activity of bacterial cells and impede further course of the reaction. An attempt was, therefore, undertaken in this study to determine which concentrations of glycerol (30, 50, 70, 100 g L^?1) and DHA (10–100 g L^?1) may inhibit the growth of acetic acid bacteria of G. oxydans ATCC 621 species. Cultures of this strain were run in the Bioscreen C MBR apparatus on experimental culture media with various initial concentrations of glycerol and DHA. Analyses were also carried out to examine the impact of pH (5.0, 7.0, 8.0) of glycerol-containing culture media on cell growth of the analyzed strain G. oxydans. None of the applied substrate concentrations was inhibiting cellular divisions of G. oxydans bacteria. The initial glycerol concentrations that enabled rapid cellular divisions reached 50 g L^?1 in the medium with pH 5.0 (coefficient of specific growth rate μ = 0.0550) and 70 g L^?1 in the medium with pH 7.0 (μ = 0.0556). DHA was shown to inhibit the mitotic activity of G. oxydans bacteria even at low concentrations (20–30 g L^?1), whereas at the concentration of 70 g L^?1, it made cell divisions impossible. The applied pH values of the culture media did not inhibit the growth of G. oxydans strain.     

Preconcentration and Simultaneous Analysis of Benzimidazole Anthelmintics in Milk Samples by Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction and High-Performance Liquid Chromatography

The proposed ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) coupled with high-performance liquid chromatography-photodiode array detection (HPLC-PDA) has been developed for the preconcentration and simultaneous analysis of five benzimidazole anthelmintics. Dichloromethane (extraction solvent) and Triton X-114 (emulsifier) was used for extraction of the target analytes. The parameters affecting the extraction efficiency were investigated and optimized. Under the optimum conditions, linearity was in the range from 10 to 150 μg?L^?1 with good coefficients of determination (R ²) higher than 0.994. Preconcentration factors were obtained up to 60, corresponding to limits of detection range of 1.8???3.6 μg?L^?1. Intra-day (n?=?5) and inter-day (n?=?4?×?3) precisions were obtained with relative standard deviation of retention time and peak area below 0.8 and 9.2 %, respectively. Good recoveries for the spiked target anthelmintics at different concentrations (e.g., 20, 50, and 100 μg?L^?1) of milk samples were obtained in 72.5–113.5 %. The results demonstrated that the proposed UASEME-HPLC-PDA can be used as an alternative powerful method for the simultaneous determination of the target analytes in milk samples.     

A Cassava Starch–Chitosan Edible Coating Enriched with <Emphasis Type="Italic">Lippia sidoides</Emphasis> Cham. Essential Oil and Pomegranate Peel Extract for Preservation of Italian Tomatoes (<Emphasis Type="Italic">Lycopersicon esculentum</Emphasis> Mill.) Stored at Room Temperature

The effect of edible cassava starch–chitosan coatings incorporated with rosemary pepper (Lippia sidoides Cham.) essential oil and pomegranate peel extract on the shelf-life of tomatoes during storage at 25 °C for 12 days was investigated. Sixteen formulations, containing 10 g L^?1 cassava starch and various concentrations of chitosan (5, 10, 20, 30 g L^?1), essential oil (0, 2.5, 5, 10 mL L^?1) and pomegranate peel extract (0, 5, 10, 20 mL L^?1) were prepared and applied to tomatoes. Physical–chemical and microbiological analyses were performed on days 1, 4, 8 and 12. Most of the coatings delayed the ripening of tomatoes, lowering the total soluble solids (38?44 g sucrose kg^?1) and weight loss (93?128 g kg^?1) and maintaining constant firmness compared to the uncoated tomatoes (45 g sucrose kg^?1, 175 g kg^?1) at 12 days of storage. Conversely, except red intensity (a*), which was higher for the uncoated samples, the colour parameters (L*, b*) of the coated and control tomatoes were similar at the end of storage. Uncoated and coated tomatoes showed no contamination during storage. The coatings showed potential to maintain the quality of tomatoes during storage at 25 °C for 12 days. In this context, tomatoes coated with the formulation comprising 10 g L^?1 cassava starch, 10 g L^?1 chitosan, 10 mL L^?1 essential oil and 20 mL L^?1 pomegranate peel extract showed the lowest weight loss and reduced total soluble solids content compared with uncoated ones.     

Micellar Electrokinetic Chromatography Method for Determination of the Ten Water-Soluble Vitamins in Food Supplements

The separation and determination of the ten water-soluble vitamins by using capillary electrophoresis in the micellar electrokinetic chromatography in a single run are proposed. The method uses low toxicity and cost solvent (ethanol) as modifier of background electrolyte (BGE) attending to the Green Chemistry principles. The electrophoretic method uses 10.0 % (v/v) ethanol, 2.0 % (w/v) SDS, 0.02 mol?L^?1 borate at pH 8.70 as BGE. The standard and real sample solutions were injected in the eletrophoretic system by hydrodynamic injection under pressure of 0.80 psi for 8 s, and the separation was carried out in a fused silica capillary under a potential of 28 kV at 25 °C; the analytical signals were monitored at 214 nm. The analytical method is precise (r.s.d.?<?6 %), accurate (better than 9 %), selective, sensitive, robust, simple, and presents high analytical frequency as ten water-soluble vitamins were separated in only 18 min, with migration times of 5.75?±?0.02, 6.81?±?0.02, 8.13?±?0.04, 8.80?±?0.07, 8.98?±?0.06, 11.10?±?0.08, 11.34?±?0.05, 13.85?±?0.15, 14.82?±?0.04, and 17.85?±?0.30 min. Detection and quantification limits of 0.34, 0.32, 0.27, 0.20, 2.50, 4.98, 4.92, 0.30, 0.86 and 0.28 mg?L^?1 and 1.02, 0.97, 0.83, 0.62, 7.56, 15.09, 14.91, 0.90, 2.59 and 0.83 mg?L^?1, for vitamins PP (nicotinamide), B₁₂ (cyanocobalamin), B₂ (riboflavin), B₆ (pyridoxine), B₈ (biotin), C (ascorbic acid), B₅ (pantothenic acid), B₃ (nicotinic acid), B₁ (thiamine), and B₉ (folic acid), respectively. Excellent recoveries (intra and inter-day) were obtained and, when the method was applied to food supplement analyses the results were in agreement with the conventional HPLC methods.     

Determination of Major Sialic Acids in Dairy Products by Electrophoretic Stacking Technology with Contactless Conductivity Detection

Synergistic stacking technique by combining field-amplified sample injection with moving chemical reaction boundary was developed for the sensitive determination of two major sialic acids, N-acetylneuraminic acid (NANA) and N-glycolylneuraminic acid (NGNA) based on capillary electrophoresis with capacitively coupled contactless conductivity detection. A series of experimental parameters affecting electrophoretic separation, detection sensitivity, and hydrolysis efficiency of sialic acids were investigated. Under the optimum conditions, NANA and NGNA could be well separated from the common monosaccharides and disaccharides as well as other potential coexisting inorganic and organic anions in a running buffer of 30 mmol L^?1 NaOH–10 mmol L^?1 Na₂HPO₄/0.8 mmol L^?1 CTAB. This developed method has been applied to determine the target analytes in dairy products. In terms of its high sensitivity (LODs 1.7–2.2 ng mL^?1, namely, 5.5–7.2 nmol L^?1), good linearity (r > 0.999), acceptable recovery (93–107%), and reliability of acid hydrolysis step, this proposed method provides a simple, rapid, sensitive, and environmentally friendly alternative for the analyses of the main sialic acids in dairy products without derivatization.     

Integral utilisation of barley husk for the production of food additives

A new and effective chemical–biotechnological process for the global utilisation of barley husk (obtained from the spent grains in the brewing process) is reported. With the proposed process the three main components of the lignocellulosic residue (cellulose, hemicellulose and lignin) are utilised. A first treatment with sulfuric acid (pre‐hydrolysis) allowed the solubilisation of hemicelluloses to give xylose and glucose‐containing liquors (suitable to make fermentation media for the continuous lactic acid (LA) production with L. pentosus) and a solid phase containing cellulose and lignin. In this set of experiments, a maximum volumetric productivity (Q_P) = 2.077 g L^?1 h^?1 and product yield (Y_P/S) = 0.62 g g^?1 were obtained for a dilution rate of 0.01 h^?1. The solid residues from pre‐hydrolysis were treated with NaOH in order to increase their cellulase digestibility, and dissolve the lignin content. The cellulose residue was used as substrates for lactic acid production by simultaneous saccharification and fermentation (SSF) in media containing Trichoderma reesei cellulases and Lactobacillus rhamnosus cells using the complete MRS broth or a cheaper medium. In both cases similar LA concentrations and volumetric productivities were achieved (P = 73.4–71.0 g L^?1 and Q_P = 1.28–1.25 g L^?1 h^?1, respectively), where P is LA concentration. The lignin solution obtained after the alkaline treatment was extracted with ethyl acetate in order to obtain the phenolic components. The extract obtained at pH 3 showed three times more antioxidant activity than the one extracted at pH 12.8, with an EC₅₀ of 1.396 g L^?1 for pH 3 and 4.604 g L^?1 for pH 12.8. The best extracts showed twice antioxidant activity than BHT. Copyright © 2007 Society of Chemical Industry     

The Effects of Ultrasound Treatment and Nano-zinc Oxide Coating on the Physiological Activities of Fresh-Cut Kiwifruit

This study evaluated the efficacy of ultrasound treatment and nano-zinc oxide (ZnO) coating individually and in combination in preserving the quality of fresh-cut kiwifruit. The nano-ZnO coating solution was prepared by mixing the ZnO nanoparticles in premixed chitosan–acetic acid solution. The fresh-cut kiwifruit were dipped in NaClO solution (50 μL?L^?1 sodium, control), subjected to ultrasound treatment (40 KHz, 350 W, 10 min), or coated with nano-ZnO solution. The fresh-cut kiwifruit samples were also subjected to combined ultrasound treatment and nano-ZnO coating. All of these test samples were stored at 4 °C for 10 days. The effects of these treatments on the quality parameters such as the production of carbon dioxide and ethylene, mass loss, and flesh firmness were investigated. At the end of storage, the combination treatments with ultrasound treatment at 40 KHz with 1.2 g?L^?1 nano-ZnO coating showed lower production of ethylene (1.86 μL?kg^?1?h^?1) and carbon dioxide (10.01 mg?kg^?1?h^?1), water loss (0.46 %), and texture (7.87 N). Hence, it was concluded that the combination of ultrasound treatment with nano-ZnO coating is a promising approach to extend the shelf-life of fresh-cut kiwifruit.     

The effects of the rate of addition of formic acid and sulphuric acid on the ensilage of perennial ryegrass in laboratory silos

Perennial ryegrass was ensiled in laboratory silos after addition of formic acid (850 g kg^?1) or sulphuric acid (906 g kg^?1) at rates of 0, 2, 4 and 6 litres t^?1 fresh grass. Silos were opened after 6, 18 and 90 days and the silage subjected to chemical and microbiological analysis. The untreated control was poorly fermented with a final pH of 4.7, a butyric acid concentration of 19 g kg^?1 dry matter (DM) and an NH₃-N content of 275 g kg^?1 total nitrogen (TN). For the formic acid treatments the 2 litre t^?1 and 6 litre t^?1 levels both produced well-preserved silages but they were of different types. The silage treated with 2 litre t^?1 had a pH of 4.0, a lactic acid concentration of 92 g kg^?1 DM and 161 g NH₃-N kg^?1 TN, whereas with the 6 litre t^?1 treatment, fermentation had been severely restricted. The pH was 4.2, the lactic acid concentration was only 8 g kg^?1 DM and the NH₃-N content was 80 g kg^?1 TN. However, formic acid at 4 litre t^?1 produced a badly fermented silage of final pH 5.0 with lactic acid and butyric acid concentrations of 16 and 15 g kg^?1 DM, respectively, and an NH₃-N content of 149 g kg^?1 TN. Sulphuric acid at 2 and 4 litres t^?1 produced silages of low lactic acid contents, 36 and 24 g kg^?1 DM, and they also contained butyric acid in concentrations of 13 and 11 g kg^?1 DM; respective NH₃-N contents were 206 and 114 g kg^?1 DM. When sulphuric acid was added at 6 litres t^?1, despite a reduction in the pH of the grass to 3.5, fermentation was not restricted as it was with the equivalent level of formic acid. Lactic acid was present at 27 g kg^?1 DM and the ethanol concentration was very high at 66 g kg^?1 DM; the sulphuric acid-treated silages were characterised by high yeast counts. At the higher rates of addition, formic acid reduced the.     

Determination of Polyphenol Content by Formation of Unstable Compound Using a Mini-Pump Multicommutation System

This article describes a multicommuted flow procedure for photometric determination of the polyphenol content in wines and teas, exploiting the formation of unstable intermediate products, by the reaction of sodium hypochloride with gallic acid. Because the lifetime of the formed compound is very short, a special flow cell was designed in order to enable mixing of sample and reagent solution within the flow cell, thus allowing signal monitoring, while compound formation proceeded. The flow system manifold comprised three solenoid mini-pumps to propel sample, reagent solution, and carrier fluid. The photometer consisted of a photodiode and a light emitting diode (LED) with maximum emission at 490 nm. Under the selected operational conditions, useful features including a linear response ranging from 62 to 1000 mg L^?1 gallic acid solution (R?=?0.9987), a detection limit of 21 mg L^?1 gallic acid, a sampling rate of 120 determinations per hour, a relative standard deviation of 1.9 % (n?=?20) for a typical solution containing 400 mg L^?1 gallic acid, and a waste generation of 1.0 mL per determination were also achieved. Medium recovery values of 96.2?±?10.4 and 101.9?±?7.3 % for wines and teas, respectively, were achieved.     

Simultaneous Detection of Azodicarbonamide and the Metabolic Product Semicarbazide in Flour by Capillary Electrophoresis

In the present work, capillary electrophoresis (CE) was used for the first time for the simultaneous analysis of azodicarbonamide (ADA) and semicarbazide (SEM), and the capillary electrophoresis separation conditions, extraction agents, and derivatization conditions were investigated. In 20 mmol L^?1 sodium tetraborate, 30 mmol L^?1 β-cyclodextrin (β-CD), 17 % isopropanol (v/v), and 25 mmol L^?1 sodium dodecyl sulfate (SDS) running buffer, ADA and SEM previously derivatized with 9-fluorenylmethyl chloroformate (FMOC) were separated in less than 25 min with good sensitivity. The linear ranges were 8.3?×?10^?4～6.6?×?10^?2 mmol L^?1 and 1.9?×?10^?3～3.4?×?10^?2 mmol L^?1, and detection limits (S/N?=?10) were 0.5 and 0.15 mg kg^?1 for ADA and SEM, respectively. The proposed method was successfully applied for the simultaneous analysis of ADA and SEM in five flour samples with satisfactory recovery data from 88.0 to 93.0 % for ADA and 98.0 to 106.0 % for SEM, indicating the valuable potential application of this method for food analysis.     

Effect of combined treatment of hydrolysis and polymerization with transglutaminase on β-lactoglobulin antigenicity

The effect of combined treatments of hydrolysis with different proteases, and subsequent polymerization with transglutaminase on the antigenic activity of β-Lg was studied. For the hydrolysis of β-Lg using Alcalase, Neutrase or bromelain, the reaction conditions were 3?% β-Lg and enzyme:substrate 25?U?g^?1 of protein, as was defined using factorial study. Under these conditions, the degree of hydrolysis (DH) of the hydrolysates was 12.6?% when obtained with Alcalase and approximately 4?% with Neutrase or bromelain. Post-hydrolysis polymerization did not result in an increase in molecular mass of the protein, but these samples presented a lower DH, determined by trinitrobenzenosulfonic acid (TNBS) method, suggesting that polymerization had occurred. Hydrolysis with the three enzymes reduced the β-Lg antigenicity, as evaluated by ELISA and immunoblotting analyses. The IgE-binding responses were practically null (<9?μg?mL^?1), 22.82 and 55.73?μg?mL^?1 towards the hydrolysates obtained with Alcalase, bromelain, and Neutrase, respectively. The post-hydrolysis polymerization increased or had no significant effect (P?≥?0.05) on the antigenic response of the hydrolysates.     

Use of Multivariate Optimization to Develop Methods for Direct Copper and Lead Determination in Breast Milk by Graphite Furnace Atomic Absorption Spectrometry

A direct method for lead and copper determination in breast milk by graphite furnace atomic absorption spectrometry, using aqueous calibration, was proposed in this study. Samples were diluted with hydroximethylaminomethane 80 %?v/v, pH 8. The dilution determination for Pb and Cu was 1:1 and 1:9, respectively. Fractional factorial (2^4?1) and central composite designs were used to optimize experimental conditions (pyrolysis and atomization temperatures, pyrolysis time, and modifier) using 10 μL samples introduced into a graphite furnace. The methods allowed for copper and lead determination under optimized conditions with an aqueous calibration curve between 0 and 180 μg L^?1 for Cu and 0 and 48 μg L^?1 for Pb. The detection limits were 0.92 μg L^?1 and 6.4 μg L^?1 for Pb and Cu, respectively. Intra and inter-assay studies revealed coefficients of variation of 5.0 and 6.3 %, and 6.4 and 5.5 % for Pb and Cu, respectively. Recovery studies at three concentration levels (three consecutive days, n?=?7/day) presented results between 107 and 109 % for Pb and 102 and 103 % for Cu. Good accuracy was obtained for both metals through recoveries studies using certified reference material (infant formula NIST® 1846). The method determined lead and copper in six samples and the concentrations ranged from 2.90 to 27.9 μg L^?1 for Pb and 384 to 1,212 μg L^?1 for Cu. While copper is an essential element, lead has no nutritional function and is cumulative at low concentrations. Therefore, safe, efficient, and validated methods should be available to determine its concentration in breast milk.     

Batch kinetics and modelling of ethanolic fermentation of whey

The fermentation of whey by Kluyveromyces marxianus strain MTCC 1288 was studied using varying lactose concentrations at constant temperature and pH. The increase in substrate concentration up to a certain limit was accompanied by an increase in ethanol formation, for example, at a substrate concentration of 10 g L^?1, the production of ethanol was 0.618 g L^?1 whereas at 50 g L^?1 it was 3.98 g L^?1. However, an increase in lactose concentration to 100 g L^?1 led to a drastic decrease in product formation and substrate utilization. The maximum ethanol yield was obtained with an initial lactose concentration of 50 g L^?1. A method of batch kinetics was utilized to formulate a mathematical model using substrate and product inhibition constants. The model successfully simulated the batch kinetics observed at S₀ = 10 and 50 g L^?1 but failed in case of S₀ = 100 g L^?1 because of strong substrate inhibition.