Photosensitized amino acid degradation in the presence of riboflavin and its derivatives

The addition of photosensitizers to water can accelerate disinfection in sunlight-based systems by enhancing oxidation of target compounds through direct reaction with the excited sensitizer or through production of another oxidant, such as singlet oxygen (1O?). The kinetics of the oxidation of selected amino acids in the presence of the sensitizer riboflavin (Vitamin B2), its primary photoproduct lumichrome, and its derivative riboflavin tetraacetate (2',3',4',5'-tetraacetylriboflavin; RTA) were quantified and the mechanisms of reaction were determined during exposure to 365 ± 9 nm light. 1O?-mediated reactions contributed to the rapid photodegradation of the four amino acids, but its contribution was sensitizer-dependent and varied from 5.4-10.2% for tyrosine, 7.1-12.4% for tryptophan, 18.7-69.0% for methionine, and 64.7-100.2% for histidine. Riboflavin was subject to rapid photodegradation (t? < 8 min), while the half-lives of lumichrome and RTA were 100 and 30 times longer, respectively. Lumichrome and RTA also were more efficient 1O? sensitizers (quantum yield (Φ) = 0.63 and 0.66) compared to riboflavin (Φ = 0.48). Of the three flavin-based compounds, RTA shows the most promise as a sensitizer in sunlight-based disinfection systems because it absorbs both visible and UV light, is an efficient 1O? sensitizer, is a strong oxidant in its triplet state, and exhibits greater photostability.     

Kinetic analysis of the loss of some B-vitamins during the cooking of macaroni

The kinetics of the losses of thiamin, niacinamide, and riboflavin were investigated during the cooking of macaroni at 50, 75, 80, 85, and 90 °C. Simultaneous analysis of the vitamins was achieved by HPLC using a μ-Bondapak column. The activation energies for the losses of thiamin, niacinamide, and riboflavin were determined as 25 kJ/mol, 22 kJ/mol, and 11 kJ/mol, respectively. It was concluded that the leaching of these vitamins into cooking water was the main pathway for their loss during macaroni preparation.     

Effects of Water Activity, Light Intensity and Physical Structure of Food on the Kinetics of Riboflavin Photodegradation

The kinetics of light-induced riboflavin degradation were evaluated in elbow macaroni, particulate macaroni, nonfat dried milk, skim milk and a buffered solution of riboflavin. A first order degradative mechanism was observed in liquid systems, while a two-phased mechanism was observed in dry food systems. Light intensities of 25, 50 or 100 ft-c showed no significant differences in effect on the rate of riboflavin loss in elbow macaroni; however, a very dim light showed only a single-phased first order rate of loss. In elbow macaroni exposed to a broad range of water activities the degradation of riboflavin increased at elevated relative humidities. Lumichrome was determined to have limited use as a quantitative indicator of riboflavin loss, but could be used as a qualitative indicator of riboflavin degradation.     

A study on degradation kinetics of riboflavin in green gram whole (Vigna radiata L.)

The kinetics of riboflavin degradation in green gram whole (Vigna radiata L.), as well as in pure riboflavin solutions, at initial concentrations present in green gram were studied over a temperature range of 50–120 °C (steady state temperature process). Riboflavin degradation followed first order kinetics, where the rate constant increased with an increase in the temperature. The temperature-dependence of degradation was adequately modelled by the Arrhenius equation. The degradation kinetics of riboflavin, in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient `Eco-cooker', were also studied (unsteady state heating process). A mathematical model, to predict the losses of riboflavin from the time–temperature data of the unsteady state heating/cooking process, has been developed using the steady state kinetic parameters obtained. The results indicate riboflavin degradation of a similar magnitude in all three modes of cooking used in the study.     

Influence of Nitrogen and Carbon Sources on Riboflavin Production by Wild Strain of Candida sp.

Microorganisms are capable of producing vitamins as metabolites, which are essential nutrients, in the metabolism of energy production. So, microbial production has been researched for years. Riboflavin is one of the fewest B-vitamins biotechnologically produced. There are many factors that affect riboflavin biosynthesis, which varies in each microorganism. However, few studies of the effect of different carbons and nitrogen sources on riboflavin production have been done. Thus, our objective in this study was to work on the effect of previously selected carbon and nitrogen sources on riboflavin production by screened wild-type yeast Candida sp. LEB 130. Classical shaken fermentation vessel system was used, controlling temperature and agitation, with fixed oxygen concentration. A 2⁵ screening design was used to analyze the effect of the medium components such as sucrose, flaxseed oil, and yeast extract. A second experiment factorial design 2⁴ yielded a riboflavin production of 105.7 ug/mL, 4.2-fold higher than 2⁵ design. Riboflavin analysis was done in a spectrophotometer. Screening design as a medium performance evaluation ended up being very advantageous for riboflavin production by this yeast.     

Riboflavin and lumichrome in Dalmatian sage honey and other unifloral honeys determined by LC-DAD technique

Riboflavin (vitamin B(2)) and its metabolite lumichrome were quantified in 117 samples from 11 unifloral honeys types (Arbutus unedo L., Asphodelus microcarpus Salzm. et Viv., Citrus spp., Eucalyptus spp., Hedysarum coronarium L., Castanea sativa L. honeydew, Mentha spp., Paliurus spina-christi., Salix spp., Salvia officinalis L., Satureja spp.). The quantification of these two compounds was performed by LC-DAD method which does not require sample purification. The proposed method in our study has low limits of detection and quantification, very good linearity in a large concentration range and very good precision. It allows simultaneous determination of 5-hydroxymethylfurfural (HMF) and known chemical biomarkers of unifloral honeys such as abscisic acid diastereomers, homogentisic acid, methyl syringate and kynurenic acid. No statistical correlation was observed between riboflavin and lumichrome content. Although, the concentration of vitamin B(2) in honey may be too low (<6.1mg/kg) to generate interest in the field of nutrition, the presence of its main metabolite lumichrome may be useful to determine the botanical origin of certain unifloral honeys. In fact, the analysis of 11 unifloral honey types showed that Dalmatian sage (S. officinalis L.) honey is characterised by unusual high levels of lumichrome (20.2±2.6mg/kg). The botanical origin of lumichrome from sage flower was assessed by analysing bee-stomach extracts. Other analytical parameters, such as total phenols, antioxidant and antiradical activities, HMF and diastase activity were studied in Dalmatian sage honey.     

常压室温等离子体诱变选育高产核黄素枯草芽孢杆菌

该研究以BS120作为出发菌株,通过常压室温等离子体诱变(atmospheric and room temperature plasma,ARTP)技术进行诱变处理,第一轮以40 mg/L 8-氮鸟嘌呤为筛选拮抗物进行筛选,得到核黄素产量和得率分别提升61. 60%和58. 12%的菌株BSG1。第二轮诱变以300 mg/L寡霉素为筛选拮抗物进行筛选,筛选获得菌株BSG3,核黄素产量和得率较BS120分别提升83. 59%和78. 76%。将核黄素操纵子表达质粒pMX45转入BSG3中,得到菌株BSG5,核黄素产量达到(4 467. 08±99. 47) mg/L,得率为(42. 56±1. 25) mg/g葡萄糖,较BS120分别提高140. 94%和120. 52%,展现了良好的核黄素发酵性能和遗传稳定性。     

Separation, identification and determination of lumichrome in swine feed and kidney.

During surveillance of hog carcasses from Manitoba for antibiotic residues by the Health of Animals Laboratory, Agriculture Canada, Saskatoon, an unknown substance was found which produced tetracycline-like results with the methods used. This same substance was found in an implicated swine feed premix. Using various HPLC systems and columns, UV spectroscopy, reverse-phase TLC, and mass spectrometry, the substance was isolated from the feed premix, and identified as lumichrome, a photodegradation product of riboflavin. Traces of the same substance were found in riboflavin standard. Analysis of swine kidney, previously found to contain the unknown, showed the same substance was present at a level of about 1 ppm.     

Increased riboflavin production from activated bleaching earth by a mutant strain of Ashbya gossypii

The production of riboflavin from vegetable oil was increased using a mutant strain of Ashbya gossypii. This mutant was generated by treating the wild-type strain with N-methyl-N′-nitro-N-nitrosoguanidine (MNNG). Riboflavin production was 10-fold higher in the mutant compared to the wild-type strain. The specific intracellular catalase activity after 3 d of culture was 6-fold higher in the mutant than in the wild-type strain. For the mutant, riboflavin production in the presence of 40 mM hydrogen peroxide was 16% less than that in the absence of hydrogen peroxide, whereas it was 56% less for the wild-type strain. The isocitrate lyase (ICL) activity of the mutant was 0.26 mU/mg of protein during the active riboflavin production phase, which was 2.6-fold higher than the wild-type strain. These data indicate that the mutant utilizes the carbon flux from the TCA cycle to the glyoxylate cycle more efficiently than the wild-type strain, resulting in enhanced riboflavin production. This novel mutant has the potential to be of use for industrial-scale riboflavin production from waste-activated bleaching earth (ABE), thereby transforming a useless material into a valuable bioproduct.     

Influence of Initial Riboflavin Content on Retention in Pasta During Photodegradation and Cooking

Samples of enriched pasta were stored under controlled lighting conditions and the loss of riboflavin was determined. After an initial rapid degradation, the riboflavin level continued to decrease slowly. After 12 wk, more than 80% the riboflavin had degraded. When pasta samples- with varied levels of riboflavin enrichment were exposed to light for 2 days, riboflavin losses ranged from 57.8–64.3%. Riboflavin leaching from pasta during cooking was also shown to be concentration independent with 34.5–37.6% of the riboflavin solubilized in the cooking water. Riboflavin in pasta which had been exposed to light for 2 days prior to cooking had a similar percentage of the undegraded riboflavin leached into the cooking water.     

Antioxidant mechanisms of Trolox and ascorbic acid on the oxidation of riboflavin in milk under light

Antioxidant activities and the mechanism of water-soluble Trolox and ascorbic acid on the oxidation of riboflavin in milk were studied. Trolox or ascorbic acid at 0, 100, 250, 500, or 1000 ppm was added to milk with or without added 50 ppm riboflavin and stored under light at 27 °C. Headspace oxygen was analysed by GC and Trolox, ascorbic acid, and riboflavin were determined by HPLC. The headspace oxygen of milk with added 50 ppm riboflavin depleted faster than that of milk without added riboflavin (p < 0.05). Trolox and ascorbic acid decreased during storage under light and riboflavin was completely destroyed within 24 h. As the concentration of Trolox or ascorbic acid increased, the riboflavin loss decreased. Riboflavin, Trolox, and ascorbic acid competed to react with singlet oxygen which was formed in the presence of riboflavin under light. Trolox and ascorbic acid protected riboflavin in milk under light by reacting with singlet oxygen.     

Effect of Fluorescent Light on Repartition of Riboflavin in Homogenized Milk

This study was designed to determine the effect of fluorescent light on riboflavin in homogenized milk and in the resulting fat, casein, and acid whey isolated therefrom. The major proportion (82%) of riboflavin in homogenized milk was associated with the acid whey fraction, about 15% with the casein phase and about 3% with the fat phase. Riboflavin loss due to light exposure (2150 lx for 48 h at 7 C) was greatest in the whey fraction. Further separation of the whey proteins by gel filtration on Sephadex G-75 superfine indicated that the riboflavin associated with the high molecular weight fraction decreased following exposure. In the whey fraction, 95% of the riboflavin was in the free form and not associated with the major whey proteins. The free riboflavin was most labile to light exposure.     

Effects of Riboflavin Photosensitized Oxidation on the Volatile Compounds of Soymilk

ABSTRACT: Soymilks with or without added riboflavin in serum bottles were stored under light or in dark at 20 °C. The headspace oxygen and volatile compounds were determined by gas chromatography. Riboflavin had significant effects on the headspace oxygen depletion and volatile compounds formation in soymilk under light ( P < 0.05). Riboflavin did not have significant effects on the formation of volatile compounds and the depletion of headspace oxygen in dark ( P > 0.05). The volatile compounds increased under light, but not in dark as the added riboflavin increased. Storage temperature at 4 °C or 20 °C did not have significant difference in the effect of riboflavin on the headspace oxygen depletion in soymilk under light. Hexanal, an important beany flavor compound, was identified as the major volatile compound in the riboflavin photosensitized soymilk. Singlet oxygen oxidation was involved in the formation of volatile compounds in soymilk under light. Hexanal could be formed by singlet oxygen oxidation. Ascorbic acid, a quencher for singlet oxygen and the excited triplet sensitizer, significantly inhibited the formation of hexanal and total volatiles in soymilk under light.     

Whey protein/alginate beads as carriers of a bioactive component

Bioactive components encapsulated in gel particles offer a means to deliver these components in a time release fashion to improve health through daily diet. The objective of this work was to evaluate the physical/mechanical properties of a release system consisting of whey protein/alginate gel beads in a model beverage. Riboflavin, vitamin B₂, was incorporated in the gel beads as a model bioactive compound. Gel beads were formed both with and without riboflavin and then added to a xanthan/sucrose suspending medium. Both the beads and the polymer solutions from which they were formed were characterized by standard rheological methods. An absorbance method was used to monitor riboflavin release over time. NMR and MRI (magnetic resonance imaging) methods characterized bead integrity and the state of protons in the gel beads. The combination of whey protein and alginate formed beads with good integrity and zero order rate kinetics for the release of riboflavin. The release rate of the bioactive component was more rapid that the typical shelf life of a bottled beverage however, the work represents a step toward the design of this type of functional food through characterization of the encapsulation medium.     

Influence of milk fat, milk solids, and light intensity on the light stability of vitamin A and riboflavin in lowfat milk

Retinyl palmitate and riboflavin were quantified in milk samples exposed to fluorescent light. Effects of compositional factors were determined by comparing rates of loss of riboflavin and vitamin A in milks with different amounts of milk fat and milk solids. Upon exposure to fluorescent light, rates of vitamin A and riboflavin loss were lower in whole milk than in skim milk. Riboflavin degraded more slowly in skim milk with 1% added nonfat dry milk than in skim milk with no added solids. No additional protective effect for riboflavin was found when added solids were increased from 1 to 3%. Compared with milk with no added solids, 1% added nonfat dry milk did not increased protection for vitamin A, but a protective effect was noted when the skim milk was fortified with 3% nonfat dry milk. Increasing light intensity increased the rates of loss of both vitamins, and riboflavin was lost at a greater rate.     

Thiamin and ribovlavin status in populations of Arkhangelsk

It was been performed the epidemiological study of Thiamine and Riboflavin status of 3579 inhabitants in Arkhangelsk. Establish by 49.6% man and 47.4% woman have lower provision of thiamin. Lack of riboflavin reveal by 23.6% man and 21.7% woman. The analysis of the effect of seasonality on vitamins content shown the worst thiamin level in examined population in January-February and in September-October. The worst Riboflavin content observed in examined population in December-January and in July-August.     

Ingestion of milk fermented by genetically modified Lactococcus lactis improves the riboflavin status of deficient rats

Riboflavin deficiency is common in many parts of the world, particularly in developing countries. The use of riboflavin-producing strains in the production of dairy products such as fermented milks, yogurts, and cheeses is feasible and economically attractive because it would decrease the costs involved during conventional vitamin fortification and satisfy consumer demands for healthier foods. The present study was conducted to assess in a rat bioassay the response of administration of milk fermented by modified Lactococcus lactis on the riboflavin status of deficient rats. Rats were fed a riboflavin-deficient diet during 21 d after which this same diet was supplemented with milk fermented by Lactoccus lactis pNZGBAH, a strain that overproduces riboflavin during fermentation. The novel fermented product, with increased levels of riboflavin, was able to eliminate most physiological manifestations of ariboflavinosis, such as stunted growth, elevated erythrocyte glutathione reductase activation coefficient values and hepatomegaly, that were observed using a riboflavin depletion-repletion model, whereas a product fermented with a nonriboflavin-producing strain did not show similar results. A safety assessment of this modified strain was performed by feeding rodents with the modified strain daily for 4 wk. This strain caused no detectable secondary effects. These results pave the way for analyzing the effect of similar riboflavin-overproducing lactic acid bacteria in human trials. The regular consumption of products with increased levels of riboflavin could help prevent deficiencies of this essential vitamin.     

Riboflavin photo-transformation of genistein and changes in radical scavenging activities of photo-transformed genistein derivatives

Genistein was treated with riboflavin photosensitization and the radical scavenging activities of mixtures of genistein and riboflavin were determined using DPPH and ABTS assays. For a period of light irradiation of 100 min, the initial concentration of genistein decreased by 79.1% for riboflavin photosensitization. New peaks were formed and the peak areas increased for a mixture of riboflavin photosensitized genistein. Genistein derivatives were tentatively identified as trihydroxy isoflavones or genisteins with an additional hydroxyl groups. The radical scavenging abilities of photo-sensitized genistein derivatives were significantly (p<0.05) increased, based on DPPH and ABTS results, compared to samples without visible light irradiation for 100 min of photosensitization. Riboflavin photo-transformation can enhance antioxidant activities in isoflavone aglycones.     

浓缩核黄素发酵液制取饲料添加剂

从发酵液直接制取作为饲料添加剂的核黄素颗粒（含ＶＢ２约１０％）具有很大的实用价值。通过对重力沉降、过滤和离心等分离方法的试验，发现离心分离是去核黄素发酵液中的机械水分的好方法，而重力沉降和过滤除水在工业生产中均存在着较大的困难。离心获得的浓缩的发酵液经干燥、粉碎和筛分以后可制得流动性好，容易与大宗饲料均匀混合的核黄素颗粒。在实际生产中利用喷雾和流化干燥离心获得的发酵浓缩物将取得更为理想的效益。     

Chemical Reactions and Stability of Riboflavin in Foods

ABSTRACT: Riboflavin is relatively stable during thermal and nonthermal food processing and storage but is very sensitive to light. It can accept or donate a pair of hydrogen atoms. It can act as a photosensitizer (through either Type I or Type II mechanism) or a prooxidant for food components under light. Photosensitization of riboflavin causes production of reactive oxygen species such as superoxide anion, singlet oxygen, hydroxy radical, and hydrogen peroxide. Radicals and reactive oxygen species accelerate the decomposition of proteins, lipids, carbohydrates, and vitamins, and could cause significant nutrient loss in foods. Carbohydrates are less sensitive to riboflavinphotosensitized oxidation than proteins, lipids, or vitamins. Riboflavin is an excellent photosensitizer for singlet oxygen formation and a superb reactant for singlet oxygen, with the reaction rate of 1.01 ± 10¹⁰/M/s.