5L发酵罐产L-乳酸的优化研究

对乳杆菌亚种TL-4的5L罐发酵条件进行了研究.确定了以玉米浆10mL/L,麸皮20g/L为氮源的发酵培养基,通风12h(通风量200L/h,搅拌转速150r/min),发酵56h,以400g/L氢氧化钙为中和剂,产酸达150g/L,转化率达94.62%.并通过二次补糖的分批补料发酵方式,有效地消除了底物抑制作用,使产酸达172.5g/L,转化率达96.27%.氮源成本投入为200元/tL-乳酸左右.     

两阶段搅拌转速控制策略发酵生产柠檬酸

采用3 L机械搅拌式发酵罐研究黑曲霉发酵生产柠檬酸的培养条件,考察了不同梯度的发酵转速对黑曲霉生长、柠檬酸产量以及残糖的影响。结果显示,在固定控制条件下,固定转速500 r/min时发酵情况最好,产酸均达到12.9 g/dL,糖酸转化率为86%,生物量为42.6 g/L。根据实验结果进行了两阶段转速控制发酵,结果产酸为14 g/dL,转化率94.6%。在此基础上进行了分批补料发酵优化,与两阶段搅拌转速控制分批发酵相比,柠檬酸产量(17.2 g/L)提高了22.8%,糖酸转化率(95.5%)提高了2.2%。     

L-缬氨酸高产菌XQ-8补料分批发酵的研究

在分批发酵优化条件基础上,通过对补料分批发酵方式发酵过程的各种参数,包括产酸率、转化率和发酵周期等进行了研究,确定了L-缬氨酸高产菌XQ-8补料分批发酵的最优条件。在最优补料分批发酵条件下发酵72h左右,L-缬氨酸产量达72g/L,糖酸转化率达38%以上,其结果明显优于分批培养。     

L-天冬酰胺酶的补料分批发酵

L-天冬酰胺酶(L-Asparaginase,EC 3.5.1.1,L-ASNase)广泛应用于食品和医药领域。为实现重组L-ASNase的高产,在3 L罐水平研究了搅拌转速与补料分批发酵条件对Bacillus subtilis/ASNΔ25/B2菌体生长与产酶的影响。通过优化确定补料分批发酵条件如下:发酵0～8 h搅拌转速:700 r/min;发酵8 h后搅拌转速:900 r/min;发酵16～28 h:恒速流加(18.75 mL/h)蔗糖(800 g/L),恒速流加(32 mL/h)酵母蛋白胨(200 g/L)和玉米浆(80 g/L)混合氮源。基于以上发酵条件,L-ASNase酶活在48 h可达到1 413.6 U/mL,较分批发酵提高了66.2%,生产强度提高了24.6%。研究结果为重组L-ASNase工业化生产提供了基础数据。     

L-鸟氨酸补料分批发酵的研究

在优化了批式发酵条件的基础上,通过对流加补料方式、补料速度等发酵过程的各种参数,包括产酸率、转化率、发酵周期等进行了研究,优化了L-鸟氨酸补料分批发酵的条件。在最优补料分批发酵条件下,发酵58 h,L-鸟氨酸产量达59.35 g/L,糖酸转化率达37.09%。发酵结果明显优于分批培养。     

碳源对L-苏氨酸发酵的影响

以L-苏氨酸生产菌TRFC为供试菌株,研究了碳源对L-苏氨酸发酵的产量和糖酸转化率的影响。采用补料分批发酵工艺生产L-苏氨酸,利用氨基酸分析仪测定发酵液中L-苏氨酸的产量。确定了发酵的最佳碳源及其补料方式,通过10L罐补料分批发酵36h,产酸可达118.9 g/L,糖酸转化率为47.6%。     

L-色氨酸营养缺陷型高产菌株的发酵工艺研究

目的以L-色氨酸营养缺陷型高产菌HX22-118为出发菌株,研究探讨L-色氨酸补料分批发酵工艺。方法通过对L-色氨酸补料分批发酵工艺中不同初糖浓度、不同补料方式、碳氮源比例、不同p H值调节方式、添加L-苯丙氨酸、L-酪氨酸对发酵的影响进行了研究。结果通过补料分批发酵工艺能有效地解除了高糖对菌体生长的抑制,促进菌体生长产酸,选择初糖淀粉浓度为90 g/L,保持葡萄糖总浓度160 g/L,在发酵第24 h开始连续流加剩余的糖,并于发酵第12 h和24 h分2次补加各50 mg/L的L-苯丙氨酸、L-酪氨酸,同时用氨水与Na OH控制发酵过程的p H,发酵产酸较分批发酵的33.5 g/L提高49.5%,达到50.1 g/L,缩短了发酵周期,提高了原料利用率。结论形成一套先进的L-色氨酸工业化发酵生产工艺技术,产酸高,生产运行稳定。     

以右旋糖酐发酵废液为原料发酵生产丁二酸

以右旋糖酐发酵废液为原料利用琥珀酸放线杆菌发酵生产丁二酸,在比较不同糖浓度废液对发酵产酸影响的基础上,通过Plackett-Burman试验筛选出对摇瓶发酵产丁二酸的主要影响因素Na H2PO4·2H2O,并用单因素试验确定其最适质量浓度为2.8 g/L。在3 L发酵罐上进行分批发酵和补料分批发酵,以60 g/L初糖质量浓度的右旋糖酐发酵废液为碳源,分批发酵46.8 h产丁二酸40.5 g/L;采用30 g/L葡萄糖为起始发酵培养基的碳源,后续补加浓缩右旋糖酐发酵废液的方式进行补料分批发酵,丁二酸质量浓度达到55.0 g/L,生产强度1 g/(L·h),糖酸转化率为0.83 g/g。结果表明:以右旋糖酐发酵废液为原料发酵生产丁二酸,为解决废液处理排放提供了新途径,具有良好的应用前景。     

耐有机溶剂α-葡萄糖苷酶的补料分批发酵研究

作者研究了Bacillus licheniformis JXC-1在3 L发酵罐上产耐有机溶剂α-葡萄糖苷酶的关键因素,结果表明:p H恒定7.0,初始糖质量浓度25 g/L,搅拌转速600 r/min为最适产酶条件,酶活由104.6 U/L提高到了444.7 U/L。通过4种补料策略对其进行补料分批发酵研究,得出:4~5 h内补料速度为2.25 m L/h,5~6 h内补料速度为6.75 m L/h,6~7 h内补料速度为9 m L/h,7~8 h内补料速度为15 m L/h补加麦芽糖与蛋白胨效果最好,酶活达到872.5 U/L。     

分批补料高密度培养米根霉As3.819产L-乳酸的研究

采用分批补料方式对米根霉As3.819高密度培养产L-乳酸的效果进行研究。摇瓶实验确定的最佳培养条件为：接种量5%、接种时间24h、装液量40%、补料液中葡萄糖与硫酸铵的质量比为20:1。罐发酵的最佳补料方式为葡萄糖浓度反馈流加。通过流加培养获得了较高的菌体密度,菌体干重达18.45g/L;重复发酵5批次,产L-乳酸效率达2.25g/L·h;菌体干重和产酸效率较分批培养分别提高了92.9%和82.9%。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.