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     

提高糟烧白酒产品质量和出酒率的探讨

糟烧白酒是生产黄酒的副产物-酒糟,经湿热作用蒸馏而得的酒精饮料。产品主要成份来自黄酒发酵醪经压榨后的糟粕截留下来的酒精等成份或酒糟经二次固态发酵时,加上残存微生物所分泌的各种酶类水解残余淀粉、蛋白质及酒精、乳酸等先液态后固态两次发酵作用的结果。加强科学研究,不断总结经验教训,是提高和进一步提高产品质量及出酒率的唯一途征。     

响应面法优化玫瑰醋糟酶解工艺

针对玫瑰醋糟组织致密,高酸性的特点,从水解度的角度出发,通过采用响应面方法对玫瑰醋糟中的大米蛋白提取过程中的温度、酶用量、pH等工艺条件进行了优化.采用Plackett-Burman(PB)设计法,对不同的酶用量、固液比、温度、时间、pH值5个因素对大米蛋白水解度的影响进行评价.结果表明:温度、酶用量、pH值为米糟蛋白提取过程中的主要影响因素,用中心组合设计及响应面分析法确定主要因素的最优条件,为温度56.8℃、酶用量1.1％、pH7.9,得到大米蛋白提取液的水解度为10.04％.     

稀酸预处理对玉米秸秆纤维组分及结构的影响

研究了稀硫酸预处理对玉米秸秆化学组成变化及纤维素酶水解得率的影响,并采用扫描电镜(SEM)、X射线衍射仪(XRD)、红外光谱(IR)和热重分析(TG)对玉米秸秆纤维结构特性进行了分析。结果表明随着硫酸浓度的增大、温度的升高和时间的延长,纤维素和木质素含量有所增加,而半纤维素含量大幅度降低,且预处理后纤维素酶水解得率也逐渐增大。当处理条件为硫酸质量分数0.75%、温度150℃、时间80 min时,半纤维素降解率为98.02%,所得固体渣纤维素酶水解得率为66.95%(纤维素酶用量20 FPUI/g纤维素)。稀酸预处理后玉米秸秆纤维表面和细胞壁受到不同程度的破坏,表面积增大,孔洞增加,纤维素的结晶度降低,有利于纤维素酶水解作用的进行。     

Combined chemical and enzymic treatments of corn husk lignocellulosics

The potential for using corn (Zea mays L) husk residues (carbohydrates 827 g kg^?1, lignin 66 g kg^?1 DM) as a carbohydrate source for the production of soluble sugars by combined chemical pretreatment and enzymic hydrolysis was assessed. Comparative investigations of acidic and alkaline pretreatments on corn husk have shown that pentose-containing carbohydrates comprised 86–93% of the solubilised fraction. While pretreatments with 1.25 M NaOH at 25.85° C resulted in preferential extraction of hemicellulose having DP; > 12, acid pretreatments 0.51 M H₂SO₄, 0.51 M H₃PO₄ at (85° C) resulted in extensive depolymerisation of this polysaccharide. Xylose and low molecular weight carbohydrates were identified as the major products. Subsequent hydrolysis of the solubilised fraction with crude hemicellulase preparations yielded 40.90% fermentable sugars. When NaOH (0.02–1.25 M), H₂SO₄ and H₃PO₄ (0.02–0.51 M) were used as pretreatment solvents (25–85° C, 2 h), NaOH was the most effective in increasing the susceptibility of the residual husk towards enzymes, yielding 83–96% reducing sugars. This solvent solubilised up to 60.6% of the lignin and appeared to disintegrate the fibrillar structure of husk. The crystallinity of husk residues increased following the chemical pretreatments and was positively correlated with cellulose content. Enzymic hydrolysis with commercial cellulase preparations proceeded in two stages: a rapid breakdown of amorphous cellulose after which the hydrolysis rate levelled off. Similar biphasic patterns were observed for the pyrolysis temperature of cellulose. Under the most optimal conditions for husk saccharification (pretreatment with 1.25 M NaOH, 25° C, 2 h, followed by enzymic hydrolysis using a mixture of cellulase and cellobiase), 96% of the cellulose-enriched residues was hydrolysed to reducing sugars. A cellulase preparation from Trichoderma reesei exhibited substantial hemicellulolytic activity and could, therefore, be used as the sole saccharifying enzyme preparation for husk lignocellulosics.     

Inhibitors of lactic acid fermentation in Spanish-style green olive brines of the Manzanilla variety

Frequently, a delay or lack of lactic acid fermentation occurs during the processing of Spanish-style green olives, in particular of the Manzanilla variety. Many variables can affect the progress of fermentation such as temperature, nutrients, salt concentration, antimicrobials in brines, and others. In this study, it was demonstrated that an inappropriate alkaline treatment (low NaOH strength and insufficient alkali penetration) allowed for the presence of several antimicrobial compounds in brines, which inhibited the growth of Lactobacillus pentosus. These substances were the dialdehydic form of decarboxymethyl elenolic acid either free or linked to hydroxytyrosol and an isomer of oleoside 11-methyl ester. Olive brines, from olives treated with a NaOH solution of low concentration up to 1/2 the distance to the pit, contained these antimicrobials, and no lactic acid fermentation took place in them. By contrast, a more intense alkaline treatment (2/3 lye depth penetration) gave rise to an abundant growth of lactic acid bacteria without any antimicrobial in brines. Therefore, the precise cause of stuck fermentation in Manzanilla olive brines was demonstrated for the first time and this finding will contribute to better understand the table olive fermentation process.     

Effect of sake lees on cheese components in cheese ripened by Aspergillus oryzae and lactic acid bacteria

More than 2,000 varieties of cheese currently exist in the world, and cheese manufacture continues to flourish. To develop the cheese ripening process, additional ingredients are used during cheese production. In this study, the effect of sake lees as an additional ingredient on the fermentation of cheese using Aspergillus oryzae (koji mold), known as koji cheese, was investigated. Aspergillus oryzae is used in the fermentation of Japanese traditional foods, such as sake and soy sauce, given its strong enzymatic activities, as well as in cheese production (i.e., koji cheese). Sake lees, a by-product of the fermentation of rice with A. oryzae and yeasts in the sake brewing process, contains various metabolites, such as amino acids. Here, supplementation with sake lees enhanced the activities of lactic acid bacteria and affected the color of the cheese. Metabolome analysis revealed that sake lees altered the balance of carbohydrates and fatty acids in the cheese. Remarkably, supplementation with sake lees enhanced the production of umami-enhancing γ-glutamyl (kokumi-active) peptides. This study suggests that a new type of cheese can be produced using A. oryzae and sake lees, and information on the synergistic effects of A. oryzae and sake lees will aid the development of cheese production.     

Prehydrolysis ofEucalyptus wood with dilute sulphuric acid: operation at atmospheric pressure

MilledEucalyptus globulus wood samples were subjected to acid hydrolysis using H₂SO₄ as catalyst. The reactions were carried out in a stirred, reflux-operated batch reactor. The effects of both catalyst concentration (in the range 3.5–10%) and hydrolysis time (0–11 h) on the concentration of arabinose, glucose, xylose, acetic acid and furfural were studied. The kinetics of xylan hydrolysis followed general trends similar to those described in earlier studies. Almost quantitative xylose recovery was achieved after 11 h of reaction time in experiments with 10% H₂SO₄. The furfural concentrations were low (0–0.44 g/L) in all the cases studied. Additional aspects relative to the selectivity of the prehydrolysis are discussed.     

生物转化木质纤维素原料生产乳酸的研究进展

以木质纤维素生物原料转化生产乳酸对节约粮食、保护环境和促进乳酸产业的发展意义重大.对纤维素生产乳酸的几个技术环节:原料预处理、酶促水解、乳酸发酵的研究进展作了概要介绍和评述.并强调提高酶解效率和降低生产成本仍是现阶段研究的主要目标,指出各种新技术的集成与优化是加快其产业化进程的必由之路.     

产L－乳酸的菌种的筛选及L－乳酸生产新途径

本实验以大豆秸秆酶解液为原料,发酵制备L- 乳酸。首先对产L- 乳酸的四株菌进行筛选,选出性能优良、糖利用率和乳酸产量均较高的干酪乳杆菌作为实验用菌种。然后对乳酸菌发酵大豆秸秆酶解液制备L- 乳酸的影响因素进行了研究,研究结果表明：干酪乳杆菌发酵的最佳接种量为10%,最适发酵温度为30℃,最佳pH 值为5.5;在发酵42h 时,大豆秸秆酶解液中残留糖浓度接近于零,此时,随底物浓度的增高,乳酸产量相应增加,并且酶解液浓度达到34.98g/L 时,乳酸生产没有受到抑制。     

汾酒酒醅有机酸的研究及酿造工艺的优化

采用高压液相色谱法分析了夏季汾酒酒醅中有机酸成分,以平板划线法分离得到夏季汾酒正常酒醅和酸度过高酒醅中的产酸细菌。研究了影响酒醅总酸度的因素进而对汾酒酿造工艺进行了优化。结果表明:酒醅中有机酸以乙酸和乳酸为主,从正常酒醅中分离到23株产乙酸细菌,5株产乳酸细菌,从酸度过高酒醅中分离到22株产乙酸细菌,29株产乳酸细菌。酒醅酿造的环境温度、入缸水分和装料量对酒醅总酸度影响较大。在此基础上,通过响应面试验,得到了适宜酸度的汾酒酿造条件,即环境温度20℃、入缸水分51%、装料量0.83 kg,出缸酒醅的总酸度为2.12(0.1 mol NaOH mL/g酒醅),与模型的预测值2.07基本相符。上述结果为解决汾酒夏季生产酒醅酸度过高问题提供了科学依据。     

A comparison of the insoluble residues produced by the Klason lignin and acid detergent lignin procedures

Two methods—Klason lignin (KL) and acid detergent lignin (ADL)— for determining lignin concentration in plants were compared using stem material from lucerne (Medicago sativa L), cocksfoot (Dactylis glomerata L) and switchgrass (Panicum virgatum L), at three stages of maturity, and leaf samples from lucerne and cocksfoot. For all forages, KL values were higher than ADL values. Lucerne samples, which had crude protein levels twice that of the grass species, had KL values that were only 30–40% higher than ADL values; in grasses, KL values were 200–300% greater than ADL values. The addition of nitrogenous materials (bovine serum albumin, lysine, and ammonium sulfate) to commercial xylan and cellulose did not result in additional KL residue. Pyrolysis-GC-MS revealed that both residues appeared to be similar to the orginal plant lignin and did not appear to be contaminated with carbohydrate or protein. The higher values for grass KL residues were not due to protein con- tamination or incomplete hydrolysis of carbohydrates, but were more likely due to the solubilization of lignin components by the ADL treatment. KL values may give a more accurate quantification of the total lignin within forage plants.     

The simultaneous saccharification and fermentation of malt dust and use in the acidification of mash

In brewing, the mash or wort is frequently acidified by the addition of lactic acid or the bioacidification of the mash. The present study provides an alternative approach for mash or wort acidification by the simultaneous saccharification and fermentation (SSF) of malt dust. In this method, fermentable carbohydrates released by the enzymatic breakdown of the cellulosic portion of the malt dust are converted to lactic acid by lactic acid bacteria. The effect of temperature, ranging between 45 and 51°C, solid loading of malt dust at 2, 5 and 10% (w/v) on a dry basis, and enzyme loading at 0.65, 2.6 and 6.5 filter paper units (FPU) per gram malt dust on SSF and change in pH in mash acidification were examined. The final pH and lactic acid concentration and final glucose concentration of the SSF media were significantly affected by the temperature of the process (p < 0.05). The highest lactic acid titre (9.7 g/L) and the lowest pH (3.12) were obtained by SSF of 10% (w/v) malt dust at 45°C with 6.5 FPU/g. The pH of the mashing solution [containing 20% (w/v) ground malt] decreased to around 5.4 and 5.2 after adding 1.9 and 2.9% of SSF media with pH 3.39. © 2019 The Institute of Brewing & Distilling     

pH值对乳酸菌生长和乳酸产量的影响

研究了分别用HCl和乳酸调节培养基初始pH以及在发酵过程中加入不同的酸中和剂对乳酸菌生长和乳酸产量的影响。结果表明 ,终产物乳酸的积累是抑制乳酸菌生长和导致乳酸产量下降的直接原因 ,该情况随发酵液中H+浓度的升高 (即pH的降低 )而增强 ,H+的积累对菌体生长和产酸的影响是间接的 ;用CaCO3 调节发酵液pH优于用NaOH和NH4OH。     

Fermentation of Lye-treated Carrots by Lactobacillus plantarum

Sodium hydroxide treatment of peeled and trimmed carrots was investigated to rid them of natural epiphytic microflora that interferes with fermentation. It also formed a buffered brine by subsequent neutralization with acetic acid. Two lye concentrations (1% and 2% NaOH) and three treatment times (1,15 and 30 min) were evaluated. Inoculation of Lactobacillus pluntarum into NaOH-treated carrot brines resulted in a controlled fermentation yielding lactic acid almost exclusively. Percent carbon recovery varied from 83.7 to 148.3. More than 92% of available glucose and >85% fructose, but <13% sucrose, were utilised after 7 days fermentation. Texture and surface color (L*) of fermented NaOH-treated carrots were affected (p < 0.05) by NaOH concentration and treatment time. The product flavor was not adversely affected by alkaline treatment.     

Effects of selected lactic acid bacteria on the characteristics of amaranth sourdough

BACKGROUND: As the processing of amaranth in baked goods is challenging, the use of sourdough fermentation is a promising possibility to exploit the advantages of this raw material. In this study the fermentation properties of Lactobacillus plantarum, Lactobacillus paralimentarius and Lactobacillus helveticus in amaranth‐based sourdough were examined in order to validate them as starter cultures. pH, total titratable acidity (TTA) and lactic/acetic acid ratio of the sourdough and sensory properties of the resulting wheat bread were evaluated using fermentation temperatures of 30 and 35 °C. RESULTS: While fermentation pH, TTA and lactic acid concentration showed small variations with the use of L. plantarum and L. paralimentarius, L. helveticus reached the most intensive acidification after initial adaptation to the substrate. Acetic acid production was independent of lactic acid metabolism. Furthermore, the lactic/acetic acid ratio exceeded recommendation by 10–35 times (fermentation quotient 25–82). Sensory evaluation showed no significant differences between the two fermentation temperatures but differences among the three micro‐organisms. CONCLUSION: The results provide relevant information on the fermentation properties required of a customised starter for amaranth flour. Copyright © 2010 Society of Chemical Industry     

Improvement of L(+)‐lactic acid production from cassava wastewater by Lactobacillus rhamnosus B 103

BACKGROUND: L (+)‐Lactic acid is used in the pharmaceutical, textile and food industries as well as in the synthesis of biodegradable plastics. The aim of this study was to investigate the effects of different medium components added in cassava wastewater for the production of L (+)‐lactic acid by Lactobacillus rhamnosus B 103. RESULTS: The use of cassava wastewater (50 g L^?1 of reducing sugar) with Tween 80 and corn steep liquor, at concentrations (v/v) of 1.27 mL L^?1 and 65.4 mL L^?1 respectively led to a lactic acid concentration of 41.65 g L^?1 after 48 h of fermentation. The maximum lactic acid concentration produced in the reactor after 36 h of fermentation was 39.00 g L^?1 using the same medium, but the pH was controlled by addition of 10 mol L^?1 NaOH. CONCLUSION: The use of cassava wastewater for cultivation of L. rhamnosus is feasible, with a considerable production of lactic acid. Furthermore, it is an innovative proposal, as no references were found in the scientific literature on the use of this substrate for lactic acid production. Copyright © 2010 Society of Chemical Industry     

Cogeneration of cellobiose and glucose from pretreated wood and bioconversion to lactic acid: a kinetic study

Samples of Eucalyptus globulus wood were subjected to sequential treatments of delignification and swelling, and the solid residues were hydrolysed with a cellulase complex deficient in beta-glucosidase activity. In experiments carried out at 45 degrees C, the highest cellulose conversion (61.9%) was achieved in media containing 28 filter paper units/g using a liquor/solid ratio of 30 g/g. Models for the generation of cellobiose and glucose were developed assuming two sequential reactions (conversion of cellulose into cellobiose and hydrolysis of cellobiose to glucose) with end-product that results in competitive inhibition. Selected regression parameters were correlated with the operational conditions by means of empirical models (including linear and interaction terms) and a generalized calculation procedure that allows a close reproduction of data and shows a satisfactory ability for quantitative predictions was developed. Further experiments were carried out to study the bioconversion of hydrolysates by Lactobacillus delbrueckii into lactic acid. The kinetic modelling of the fermentation stage allowed a close interpretation of the experimental data.     

Phytate degradation by Bifidobacterium on whole wheat fermentation

Whole cereal-based products have a beneficial effect on health, but they also contain high levels of phytate, defined as anti-nutrient. The possible use of different strains of bifidobacterial species (B. catenulatum, B. longum and B. breve) with phytate degrading activity as starters in the fermentation process was investigated. Fermentative parameters of doughs (pH, volume, total titrable acidity [TTA] and acetic and lactic acids production) and the hydrolysis profile of the phytic acid were determined during whole wheat dough fermentation. During fermentation in the presence of different bifidobacterial strains, the concentration of phytic acid showed a progressive decrease, leading to a higher release of hydrolysis products than in the control, within short fermentation time. According to the fermentative parameters bifidobacterial strains showed a good adaptation to the dough ecosystem. The range of TTA and lactic acid production was dependent on the strain. Among the tested bifidobacterial strains, those belonging to the species B. breve and B. longum induced a higher hydrolysis of phytic acid with simultaneous production of lower inositol phosphates. In addition, dough containing those strains had high pH and minor acidity than those containing a commercial starter (L. plantarum). Therefore, the tested bifidobacterial strains could be used as breadmaking starters contributing to different acidification degrees and promoting simultaneously the degradation of phytic acid in the whole wheat dough.     

Effect of chemical pretreatments on the fermentation and ultimate digestibility of bagasse by Phanerochaete chrysosporium

When sugarcane bagasse was pretreated at room temperature with various chemicals singly or in combination, (0.25 m NaOH; 0.5 m H₂SO₄; 2.6 M NH₃;0.14 M Ca(OH)₂+0.12 M Na₂CO₃;4.2 m EDA; and 0.5 M H₂SO₄ or 0.25 M NaOH followed by 4.2 M EDA), increases in in-vitro digestibility range from 28.9 to 48.6% depending on the particular chemicals. With most pretreatments, the hemicellulose content decreased and the cellulose content increased slightly, while lignin levels decreased only with NaOH + EDA pretreatments. Further fermentation of the chemically pretreated bagasse with Phanerochaete chrysosporium gave increased digestibilities, the highest final digestibility (59%) being achieved by pre-treatment with 0.25 M NaOH. Pretreatment with NaOH or Ca(OH)₂+Na₂CO₃ and fermentation gave greatly increased levels of hemi-cellulose and cellulose and substantial decreases in lignin levels. Chemical pretreatments of bagasse together with autoclaving considerably enhanced in-vitro digestibility (up to 75%) and lignin degradation (1.4%). Pretreatment with NaOH, Ca(OH)₂+Na₂CO₃, and EDA plus autoclaving gave large increases in total hemicelluloses and cellulose and marked decreases in lignin. Further fermentation with P. chrysosporium gave only slight increases in digestibility.