Influence of salivary conditioning and sucrose concentration on biofilm-mediated enamel demineralization

Abstract The acquired pellicle formation is the first step in dental biofilm formation. It distinguishes dental biofilms from other biofilm types. Objective To explore the influence of salivary pellicle formation before biofilm formation on enamel demineralization. Methodology Saliva collection was approved by Indiana University IRB. Three donors provided wax-stimulated saliva as the microcosm bacterial inoculum source. Acquired pellicle was formed on bovine enamel samples. Two groups (0.5% and 1% sucrose-supplemented growth media) with three subgroups (surface conditioning using filtered/pasteurized saliva; filtered saliva; and deionized water (DIW)) were included (n=9/subgroup). Biofilm was then allowed to grow for 48 h using Brain Heart Infusion media supplemented with 5 g/l yeast extract, 1 mM CaCl2.2H2O, 5% vitamin K and hemin (v/v), and sucrose. Enamel samples were analyzed for Vickers surface microhardness change (VHNchange), and transverse microradiography measuring lesion depth (L) and mineral loss (∆Z). Data were analyzed using two-way ANOVA. Results The two-way interaction of sucrose concentration × surface conditioning was not significant for VHNchange (p=0.872), ∆Z (p=0.662) or L (p=0.436). Surface conditioning affected VHNchange (p=0.0079), while sucrose concentration impacted ∆Z (p<0.0001) and L (p<0.0001). Surface conditioning with filtered/pasteurized saliva resulted in the lowest VHNchange values for both sucrose concentrations. The differences between filtered/pasteurized subgroups and the two other surface conditionings were significant (filtered saliva p=0.006; DIW p=0.0075). Growing the biofilm in 1% sucrose resulted in lesions with higher ∆Z and L values when compared with 0.5% sucrose. The differences in ∆Z and L between sucrose concentration subgroups was significant, regardless of surface conditioning (both p<0.0001). Conclusion Within the study limitations, surface conditioning using human saliva does not influence biofilm-mediated enamel caries lesion formation as measured by transverse microradiography, while differences were observed using surface microhardness, indicating a complex interaction between pellicle proteins and biofilm-mediated demineralization of the enamel surface.

The role of human milk and sucrose on cariogenicity of microcosm biofilms

Abstract This study investigated the effect of human milk, alone and associated with sucrose, in the cariogenicity of biofilms in a microcosm biofilm model and compared with the cariogenicity of sucrose and bovine milk. Microcosm biofilms were grown in enamel discs in 24-well plates. Six growth conditions were studied: DMM (chemically defined artificial saliva - negative control), DMM with 1% of sucrose (DMM+s) (positive control), human milk with DMM, human milk with DMM+s, bovine milk with DMM, and bovine milk with DMM+s. After 5 days, the outcome variables surface hardness change (%SHC), microbiological composition of biofilms, and pH of supernatant were analyzed. All groups had significantly lower hardness loss compared to the DMM group with 1% of sucrose. Human and bovine milk associated with sucrose showed higher hardness loss. The supernatant pH values after 6 hours of different treatments were similar for the groups sucrose and human milk associated with sucrose (p>0.05). After 18 hours at rest in pure DMM, an increase in the pH of the supernatant was observed. Higher values of total microorganisms count were found for sucrose and bovine milk groups compared to the group supplemented only by DMM. Bovine milk group showed greater amount of total aciduric microorganisms in comparison to human milk group. Within the limits of this study, it can be infered that both human and cow milks have some cariogenic potential, although differing from sucrose in terms of mineral loss.

Scaling-up batch conditions for efficient sucrose hydrolysis catalyzed by an immobilized recombinant Pichia pastoris cells in a stirrer tank reactor

Background: Invert sugar is used greatly in food and pharmaceutical industries. This paper describes scaling-up batch conditions for sucrose inversion catalyzed by the recombinant Pichia pastoris BfrA4X whole cells expressing Thermotoga maritima invertase entrapped in calcium alginate beads. For the first time, we describe the application of a kinetic model to predict the fractional conversion expected during sucrose hydrolysis reaction in both, a model and a prototype bioreactor with 0.5- and 5-L working volume, respectively. Results: Different scaled-up criteria used to operate the 0.5-L bioreactor were analyzed to explore the invert sugar large scale production. After model inversion studies, a 5-L scaled-up reaction system was performed in a 7-L stirred reactor. Both scaled-up criteria, immobilized biocatalyst dosage and stirring speed, were analyzed in each type of bioreactors and the collected data were used to ensure an efficient scale-up of this biocatalyst. Conclusions: To date, there is not enough information to describe the large-scale production of invert sugar using different scaled-up criteria such as dose of immobilized biocatalyst and stirring speed effect on mass transfer. The present study results constitute a valuable tool to successfully carry out this type of high-scale operation for industrial purposes.

In vitro flowering – A system for tracking floral organ development in Dendrocalamus hamiltonii Nees et Arn. ex Munro.

Dendrocalamus hamiltonii plants are slender and tall (15-25 m) thereby, rendering tagging, sampling and tracking the development of flowers difficult. Therefore, a reproducible system of in vitro flowering was established for tracking the stages of flower development. MS medium supplemented with 2.22 µM 6-benzylaminopurine, 1.23 µM indole-3-butyric acid and 2% sucrose was optimized as the flower induction medium (FIM) wherein 28 and 42 days were required for the development of gynoecium and androecium, respectively. Six distinct stages of in vitro flower development were identified, and the flowers were comparable with that of in planta sporadic flowers. Pollen viability of the in vitro flowers was higher than those of in planta ones. The in vitro system developed in the present study facilitates easy tracking of different stages of flower development under controlled environmental conditions. It can also be used for medium- or long-term storage of pollens and manipulation of in vitro fertilization.

Invertase, glucose oxidase and catalase for converting sucrose to fructose and gluconic acid through batch and membrane-continuous reactors / Invertase de glicose oxidase e catalase para a conversão de sacarose para ácido glucónico e frutose através de lote e de membrana-contínuas reactores

Conversion of sucrose into fructose and gluconic acid using invertase, glucose oxidase and catalase was studied by discontinuous (sequential or simultaneous addition of the enzymes) and continuous (simultaneous addition of the enzymes in a 100 kDa-ultrafiltration membrane reactor) processes. The following parameters were varied: concentration of enzymes, initial concentration of substrates (sucrose and glucose), pH, temperature and feeding rate (for continuous process). The highest yield of conversion (100 percent) was attained through the discontinuous (batch) process carried out at pH 4.5 and 37 ºC by the sequential addition of invertase (14.3 U), glucose oxidase (10,000 U) and catalase (59,000 U).

Neste trabalho estudou-se a conversão da sacarose em frutose e ácido glicônico, usando as enzimas invertase, glicose oxidase e catalase, através do emprego de processo descontínuo (com adição sequencial ou simultânea das enzimas) e contínuo (adição simultânea das enzimas em reator com membrana acoplado à membrana de ultrafiltração de 100 kDa). Os parâmetros variados foram: a concentração das enzimas, a concentração inicial dos substratos (sacarose e glicose), o pH, a temperatura e a vazão específica de alimentação (processo contínuo). Obteve-se rendimento de 100 por cento, quando a conversão foi conduzida por processo descontínuo em pH 4,5 e a 37 ºC com adição seqüencial das enzimas invertase (14,3 U), glicose oxidase (10.000 U) e catalase (59.000 U).

Recovery of silver residues from dental amalgam

Dental amalgam residues are probably the most important chemical residues generated from clinical dental practice because of the presence of heavy metals among its constituents, mainly mercury and silver. OBJECTIVE: The purpose of this study was to develop an alternative method for the recovery of silver residues from dental amalgam. MATERIAL AND METHODS: The residue generated after vacuum distillation of dental amalgam for the separation of mercury was initially diluted with 32.5 percent HNO3, followed by precipitation with 20 percent NaCl. Sequentially, under constant heating and agitation with NaOH and sucrose, the sample was reduced to metallic silver. However, the processing time was too long, which turned this procedure not viable. In another sequence of experiments, the dilution was accomplished with concentrated HNO3 at 90ºC, followed by precipitation with 20 percent NaCl. After washing, the pellet was diluted with concentrated NH4OH, water and more NaCl in order to facilitate the reaction with the reducer. RESULTS: Ascorbic acid was efficiently used as reducer, allowing a fast reduction, thus making the procedure viable. CONCLUSIONS: The proposed methodology is of easy application and does not require sophisticated equipment or expensive reagents.

Micropropagation of Lilium ledebourii (Baker) Boiss as affected by plant growth regulator, sucrose concentration, harvesting season and cold treatments

A protocol for the micropropagation in different harvesting time of Lilium ledebourii (Baker) Boiss, an endangered rare species endemic to Iran has been developed. In vitro scale culture of this species, using bulbs from three harvesting seasons (spring, summer and winter), was attempted. Among the various treatments tested, the Murashige and Skoog (MS) medium supplemented with 0.1 mg l-1 naphthaleneacetic acid (NAA) + 0.1 mg l-1 benzyladenin (BA) and 6% sucrose in all harvesting seasons proved to be superior to others. The best results for fresh weight of bulblets, rooting parameters and the survival rate after transplantation to greenhouse were obtained from early winter-harvested bulbs. Summer-harvested bulbs had the highest number of bulblets per explant. The bulblets at the end of the culture period were given cold treatment at 4ºC for 2-8 weeks at a 2-weeks interval and then transplanted to a potting mixture of sand, leaf mold and peat moss (1:1:1 v/v). The best emergence rate (90%) was achieved at 8 weeks cold treatment for winter harvested bulbs.

Surgarcane biopolymer patch in femoral artery angioplasty on dogs

PURPOSE: The objective of this study was to evaluate the use of the sugarcane biopolymer membrane in femoral artery patch angioplasty on dogs. METHODS: Eight dogs were submitted to bilateral femoral artery patch angioplasty with a sugarcane biopolymer membrane patch on one side and e-PTFE patch on the contralateral side. This research was performed at Experimental Surgical Research Laboratory of the Centro de Ciências da Saúde at Universidade Federal de Pernambuco. The dogs were submitted to a new surgery at 180 days after the patch angioplasty in order to harvest the femoral artery. All the animals were evaluated by: clinical examination, measure of femoral artery diameter, arteriogram and Doppler fluxometry. Yet the material harvested was sent to histological study. Each animal served as its own control. RESULTS: In all vessels of both groups there were no cases of infection, aneurysm formation, rupture or pseudoaneurysm formation and thrombosis. In both groups it was observed a chronic inflammatory reaction with lymphocytes, neutrophils and fibrosis in the outer surface of the patches. It was observed fibrosis in the inner surfaces of all the patches. In e-PTFE patches occurred invasion by fibroblasts. CONCLUSION: The sugarcane biopolymer membrane can be used as a patch in femoral artery angioplasty on dogs.

OBJETIVO: Avaliar a utilização da membrana do biopolímero de cana-de-açúcar quando utilizada como remendo em arterioplastias femorais de cães. MÉTODOS: Oito cães foram submetidos a arterioplastia femoral bilateral com enxertos em remendo com a membrana do biopolímero de cana-de-açúcar em um lado e com a prótese de e-PTFE no lado contra-lateral. Os experimentos foram realizados no Núcleo de Cirurgia Experimental do Centro de Ciências da Saúde da Universidade Federal de Pernambuco. A avaliação dos animais foi realizada através do exame clínico, da medida do diâmetro das artérias femorais, da fluxometria Doppler, da arteriografia e da histologia. Após 180 dias os cães foram submetidos a nova cirurgia para retirada dos segmentos das artérias femorais com os implantes. RESULTADOS: No período de avaliação nos dois grupos, não se observou casos de infecção, dilatação, ruptura ou falso-aneurisma e trombose. Nos dois grupos foi encontrada uma resposta inflamatória crônica com neutrófilos, linfócitos e fibrose na superfície externa dos remendos. Foi observada também a presença de fibrose na superfície interna em ambos os grupos. No grupo controle ocorreu invasão dos remendos de e-PTFE por fibroblastos. CONCLUSÃO: A membrana do biopolímero de cana-de-açúcar pode ser utilizada como remendo em arterioplastias femorais de cães.

Genetic sensitivity to the bitter taste of 6-n propylthiouracil: a new risk determinant for dental caries in children.

The aims of the present study were to contrast the prevalence of dental caries in children with different genetic sensitivity levels to the bitter taste of 6-n-propylthiouracil (PROP) and to determine the taste quality and taste intensity preferences of food products among the taster and nontaster groups. Overall caries experience (dmfs/DMFS) was significantly higher for nontasters than tasters. Caries experience on the available surfaces (dfs/DFS) was found to be significantly higher in nontasters than in medium tasters and in medium tasters than in supertasters (r=-0.41, P < 0.001). Majority of the nontasters were sweet likers and preferred strong tasting food products, while majority of the supertasters were sweet dislikers and preferred weak tastes. There was a significant increase in the overall caries experience in the population, as the genetic ability to detect PROP taste decreased ( P < 0.001). After all associated factors (age, gender, race, number of teeth and OHI-S) were controlled; multiple linear regression analyses revealed that taste was the only variable significantly related to overall caries experience.

Effect of amino acid and protein addition on the flavour of extruded corn flour

THE AMINO acids and vegetable proteins have been recommended as safe flavouring precursors of thermal process flavouring. Therefore the present work was designed to examine the effect of such compounds on the overall qualities of corn flavour extrudates. Amino acids [proline and cysteine], vegetable proteins [soybean and gluten] and sucrose were added to corn flour pre-extrusion process. A sample free from any additives was considered as control. The sensory evaluation for each sample was carried out, the expansion ratio and protein content were determined, the results showed a significant increase in all sensory attributes comparing with the control sample. Samples containing proline or cysteine showed high quality attributes whereas addition of soybean protein or gluten resulted in significant decrease in appearance and texture attributes compared with the sample containing sucrose only. An agreement between the sensory results and expansion ratio for all samples was observed for the protein content. On the other hand, the GC and GC-MS analysis confirmed the aroma quality of each sample

Purification and characterization of an invertase produced by Aspergillus ochraceus TS.

Purification and characterization of an extracellular invertase produced by Aspergillus ochraceus TS are reported. The enzyme was purified (42-fold) from culture filtrate by salt precipitation, ion-exchange and gel filtration. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of the purified enzyme showed a single band of molecular mass 66 kDa. The molecular mass of the native enzyme was found to be 130 kDa by gel filtration. The purity of the protein was also checked against its antiserum raised in rabbits by two-dimensional immunodiffusion in agarose gel and Western blot that showed a single band. It is a glycoprotein with mannose as its carbohydrate residue. The enzyme showed high affinity for sucrose with a Km of 3.5 mM. The amino acid analysis revealed a high proportion of acidic residues but it had a low content of cysteine, histidine and arginine comparable to other fungal invertases.

Physicochemical stability of natural or pre-sweetened frozen passion fruit juice

Suco de maracujá, puro ou previamente adoçado com sacarose, 1:1 (p:v), foi congelado e armazenado por 8 meses em congeladores com temperatura de -18§C. O efeito de tempo de armazenamento e adiçäo de sacarose sobre propriedades físico-químicas foi avalidada iniciaqlmente no suco fresco e a cada dois meses nas amostras congeladas. Concentraçöes de sólidos solúveis, ácidos orgânicos, açúcares totais e redutores e ácido ascórbico, assim como pH, näo foram afetados por tempo de armazenamento. Inicialmente a adiçäo de sacarose alterou a cor do suco, mas esta se manteve durante o armazenamento, enquanto o suco natural alterou a cor para amarelo durante o armazenamento. Concentraçäo de beta-caroteno diminuiu em funçäo do tempo de armazenamento, 51,3 por cento no suco puro e 29,7 por cento no suco previamente adoçdo

Aryl beta-galactosidase from Sclerotium rolfsii: physiological and biochemical studies.

Production of beta-galactosidase by Sclerotium rolfsii NCIM 1084 was studied under submerged fermentation conditions. The enzyme was produced extracellularly and constitutively on glucose. The enzyme production was enhanced when galactose, raffinose, cellobiose, sucrose, xylose, maltose, cellulose and pectin were used as carbon sources. Cellulose and diammonium hydrogen phosphate were best carbon and nitrogen sources, respectively. Surfactants such as Sag, Paraffin oil, Tween 20 and Tween 80 increased the enzyme production. Maximum yield of beta-galactosidase obtained was 3.8-4.2 nkat/ml. The optimum pH, optimum temperature and molecular weight of the beta-glactosidase were 2.7, 60 degrees C and 2,21,000 daltons, respectively. The enzyme is an aryl beta-glactosidase and did not hydrolyse lactose. The Km value for o-nitrophenyl beta-D-galactoside was 3.7 mM. Galactose and 2-mercaptoethanol inhibited the enzyme.

Utilizaçäo da técnica tempo-intensidade na caracterizaçäo de doçura da sacarose e do esteviosídeo / Sucrose and stevioside sweetness evaluation by using the time-intensity sensory technique

Selecionou-se e treinou-se uma equipe de 10 julgadores capazes de avaliar a doçura, empregando a técnica de tempo-intensidade. Por meio da técnica de escala relativa foram determinadas as concentraçöes de 7 substâncias doces equivalentes em doçura soluçäo de 5 por cento de sacarose, obtendo-se as seguintes intensidades relativas: 1 para a sacarose, 11 para frutose, 0,5 para o sorbitol, 0,3 para a lactose, 129 para o aspartame, 23 para o ciclamato e 144 para o esteviosídeo. Com a soluçäo de de 0,034 por cento de esteviosídeo equivalente em doçura à soluçäo de 5 por cento de sacarose estudou-se a qualidade de doçura por meio da técnica tempo-intensidade. O esteviosídeo apresentou curva de intensidade de doçura em funçäo do tempo semelhante da sacarose e sabor residual doce mais persistente. Este resultado vem mostrar que a equipe do ITAL é capaz de fornecer resposta semelhante àquela descrita na literatura viabilizando o uso da técnica tempo-intensidade