30 research outputs found
Development of a Simultaneous Saccharificationand Fermentation process using alkaline pretreated wheat straw
No full textstatus: Publishe
Biofilms of Stenotrophomonas maltophilia protect Lactobacillus brevis food spoilage bacteria against classical cleaning and disinfection protocols
No full textedition: Biofilms8status: Publishe
De invloed van biofilms in de voedselverwerkingsomgeving op het bederf van ready-to-heat sauzen.
No full textFood spoilage is the microbial, chemical or physical change of a product causing it to become undesirable or unacceptable for human consumption. It is generally considered that microbial spoilage is the major cause of processed food spoilage. Microbial food spoilage is caused by a sequence of events: spoilage organisms gain access to the product; they survive and adapt to the product; and they grow to sufficiently high cell counts to cause a change in the food product.
Biofilms are consortia of bacteria adhering to a surface and enveloped in a self-produced extracellular matrix. By producing biofilms, bacteria have a higher tolerance against cleaning and disinfection protocols compared to their planktonic (free-living) counterpart and may thus survive in the food processing environment. Therefore, introduction to the food product from these biofilms is possible and the presence of biofilms is often considered as a risk for the safety and quality of the food products. Thus, the goal of this PhD research was to examine the influence of biofilms in the food processing equipment on the spoilage of food products with ready-to-heat (RTH) sauces as a case study. For this, the following approach was used: we (i) isolated the microorganisms of prematurely spoiled RTH-sauces and the food processing environment of these products, (ii) determined the biofilm-forming potential of these isolates, (iii) ascertained the biofilm tolerance against conventional cleaning and disinfection (C&D) of a selection of these isolates in a reactor model which could simulate in situ C&D conditions, (iv) checked the effect of the interactions between food spoilage bacteria, with either low or high biofilm-forming ability, and the isolates from the food processing environment on the survival of the food spoilage bacteria in the food processing equipment to (v) finally evaluate both a preventive and curative biofilm removal strategy.
In a first step, the spoilage bacteria of RTH sauces, which showed signs of premature spoilage, were isolated and identified. Three main spoilage organisms were found with different spoilage profiles. Bacilli were most often isolated and appeared to cause mild acidification and liquefaction in the RTH-sauces. Lactic acid bacteria were the second most isolated and were associated with severe acidification of the product. Finally, although only infrequently isolated, yeasts caused gas formation in the food product. The presence of bacilli in the food product might be explained by their ability to form spores which enhances their heat tolerance and might allow them to survive the heat treatment during processing of the sauces. All other spoilage bacteria, however, were not able to survive this heat treatment, indicating a secondary contamination of the sauces during filling. Moreover, the presence of biofilms in the filling equipment of these sauces was shown in a previous study, pointing to the presence of biofilms as a risk for the contamination of the RTH-sauces. However, the spoilage bacteria, isolated from the RTH-sauces, were not found among the dominant bacteria, found in biofilms in the filling equipment, indicating that even at low abundancies in the food processing environment, the spoilage bacteria might pose a risk for contamination and consequent spoilage of the RTH sauces.
Subsequently, the biofilm-forming ability of both kinds of isolates was determined in vitro. The majority of the food spoilage isolates showed some degree of biofilm formation, except a number of lactic acid bacteria. The biofilm forming ability of the isolates from the filling equipment of RTH-sauces were compared to isolates from processing equipment of other food sectors, in an attempt to find similarities between the different food sectors. However, few similarities were found among the strong biofilm producers of the different companies, except for Pseudomonas spp. and Stenotrophomonas maltophilia, which were found among the strong biofilm producers in every company except one.
To determine the biofilm tolerance against conventional cleaning and disinfection, first a laboratory method was designed to study the (organic fouling and) biofilm removal from stainless steel which could simulate in situ cleaning and disinfection conditions. This biofilm reactor model was used in the next part of the research to characterize the tolerance against cleaning and disinfection of the spoilage bacteria, isolated from the RTH-sauces, and the food processing bacteria, isolated from biofilms in the filling equipment. The spoilage bacteria were able to form biofilms on stainless steel surfaces and survive cleaning and disinfection, albeit at low initial cell counts before cleaning and disinfection and/or low tolerance against cleaning and disinfection which coincided with their (hypothesized) low abundancy in situ. In contrast, biofilms of isolates from the food processing environment showed both high initial cell counts in biofilm and high residual cell counts after cleaning and disinfection. The presence of these strong biofilm producing bacteria in the food processing environment might influence the attachment and survival of the relatively low biofilm producing food spoilage strains, which was investigated in a later step of the research. In a final step of this part, the biofilm tolerance of the strongest biofilm producers of several food companies was compared. A low efficacy of the disinfectants, without prior cleaning, was observed. However, when a cleaning step was incorporated, the efficacy of the total cleaning and disinfection protocol increased, mainly due to a high biofilm removal during cleaning. Nonetheless, differences in regrowth of the residual biofilm after (cleaning and) disinfection were observed between the different bacteria. For some bacteria the number of cells after regrowth was comparable to or higher than the initial biofilm cell count, independent of the incorporation of a cleaning step or the cleaning and disinfection products used. For one strain, the use of chlorinated products induced a higher regrowth compared to the other cleaning agents and disinfectants. For the remaining bacteria, the incorporation of a cleaning step significantly inhibited the regrowth to cell counts below the initial biofilm cell count before cleaning and disinfection, independent of the cleaning and disinfection products used. These results indicated that (i) cleaning and disinfection should be optimized against the specific bacteria isolated from the food processing environment and (ii) that further optimization of the cleaning and disinfection protocols for biofilm removal and control is still needed.
Given the low biofilm forming ability and/or tolerance against cleaning and disinfection of the food spoilage bacteria, we hypothesized that the strong biofilm producing bacteria present in the food processing environment might increase the survival of the food spoilage bacteria. Therefore, in a next step, the isolates from biofilms in the filling equipment of the RTH-sauces were pairwise cocultured with the spoilage bacteria, isolated from the RTH-sauces, to determine their interactions. For most combinations, a decrease in fitness of the spoilage bacteria, with a decrease of the total biomass and EPS production, was observed. The only exception were the combinations of food spoilage bacteria with S. maltophilia, which instead showed a positive complementary effect for all food spoilage bacteria. Therefore, these combinations were further characterized for their social interactions and tolerance against cleaning and disinfection in the biofilm reactor model, indicating a dual role of S. maltophilia on the attachment and survival of different spoilage bacteria. The fitness and tolerance against cleaning and disinfection of bacilli decreased when co-cultured with S. maltophilia, as opposed to the fitness and tolerance of lactic acid bacteria, which increased when cocultured. The presence of S. maltophilia in the food processing environment might thus both prevent or increase the risk of transmission of spoilage bacteria to the food product, dependent on the specific spoiler.
Therefore, in the final step of the research, two strategies were explored for the removal of Stenotrophomonas maltophilia biofilms. Firstly, the importance of incorporating a cleaning step for the removal of biofilms was further characterized by microscopical analysis and (partial) EPS characterization. This analysis revealed that incorporating a cleaning step induced a higher EPS removal and inhibition of the α-polysaccharides production during regrowth. Based on these results, optimization of C&D was attempted, revealing that optimal S. maltophilia biofilm removal and inhibition of the regrowth of the residual biofilm was not achieved by increasing the concentration of the cleaning agent but by increasing the disinfectant concentration after a cleaning step with the lowest concentration. Secondly, we demonstrated the potential of different modified surfaces to reduce the biofilm formation and/or facilitating the biofilm removal of Stenotrophomonas maltophilia.status: Publishe
A teacher's discourse in EFL classes for very young learners: investigating mood choices and register
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-Graduação em Letras/Inglês e Literatura Correspondente.This study reports on an ethnographic investigation about the interaction between a teacher and her very young learners in the foreign language (FL) classroom. I focus specifically on this FL teacher#s discourse as a facilitator of interactions through the analysis of her discursive practice. In order to carry out this study, data were collected in a private kindergarten school, by means of video recordings of classes in which both teacher and learners are engaged in interaction, and field notes from the teacher and from an observer. Data were analyzed through the lights of Halliday#s Systemic Functional Linguistics Mood choices and Bernstein#s pedagogic discourse regulative and instructional registers. Besides analyzing the way the children addressed the FL teacher and her use of the mother tongue, I also tried to evince the Mood structures and modality choices involved in this study, more specifically the choices made by the teacher in order to promote interactions. Moreover, the realization of the frequent use of the regulative register in terms of the teacher#s directions, suggesting acceptable behaviours was also investigated. The study is intended to contribute to make teachers of VYL aware of the role teachers# discourse to promote interactions and facilitate pedagogic practices
From wonder through evidence to probability: Darwin’s mental journey from The Voyage of the Beagle to On the Origin of Species
No full textWhen Charles Darwin’s first published On the Origin of Species in 1859 his novel ideas on evolutionary biology met with much criticism in the prevailing social context. But also his own deep-rooted Christian faith impacted the written presentation of his ideas. Following the first publication of this work five more editions by Darwin were published. These subsequent versions are marked by clear linguistic evidence of the increasing acceptance of his theory of natural selection by the author himself as well as the public. This increasingly positive reception also took place beyond the English-speaking world, through various translations in different European languages (cf. i.a. Brisset, 2002; Algoet, 2008; Vandepitte, Vandenbussche, & Algoet, 2011; Pano & Regattin, 2015). This paper will focus on the evolving expression of degrees of certainty and author commitment in Darwin’s successive six English editions of On the Origin of Species, published between 1859 and 1872, as well as the seed-bed of Darwin’s original ideas which led to the gradual development of his theory, viz. his observations during the voyage of the Beagle.
Darwin’s evolving author commitment in On the Origin of Species is examined through the expression of epistemic modality in chapter four of this work, which presents the theory of natural selection. The analysis takes a systemic-functional approach (Halliday, 1994; Halliday & Matthiessen, 2004), which considers expressions from different word classes, in addition to the closed grammatical set of English modal auxiliaries. The corpus data are based on the Online Variorum of Darwin's On the Origin of Species, which offers an aligned representation of the six British editions of the account written by Darwin. The general evolution in Darwin’s commitment to his scientific ideas is evaluated in terms of a formulaic assessment which includes seven degrees of probability and degree of objectivity as a factor of implicit versus explicit modality and objective versus subjective modality. The overall results of this analysis show an unmistakable increase of positive (69%) author commitment to the certainty of the scientific ideas expressed in the successive editions of On the Origin of Species.
The level of author commitment expressed in the final (1872) edition of On the Origin of Species came about as the culmination of a long personal mental journey from Christian faith through evidence which originated in Darwin’s observations during the second voyage of the Beagle between 1831 and 1836. The second, revised edition of Darwin’s earlier (1839) account of his observations during this journey was published in 1845 and later received the title The Voyage of the "Beagle" (1905). This second edition, made available online by the Project Gutenberg, forms the basis for the corpus of the analysis for this part of the present paper. The analysis will focus on chapter XVII of the work, which contains Darwin’s observations on the Galapagos Archipelago, and will add the category of mirativity, a linguistic category which refers to the expression of the speaker's or writer’s surprise (and which more strictly speaking refers to language systems that contain a grammatical category of mirativity for the expression of this meaning, often discussed and expressed together with evidentiality (cf. Delancey, 1997, 2001). Mirative expressions in this account (e.g. “Hence we have the truly wonderful fact, that …”, or “we feel the more astonished at …”) show us the origins of Darwin’s later scientific ideas.
Through the combined analyses of corpus data from travel literature and an ensuing scientific account and theory this paper hopes to offer an illustration of the mental journey which is often engendered by geographical travel, entailing foreign evidence of and surprise at new ways of life, with possibly transformative effect, long after the geographical journey took place.status: Publishe
The serious matter of language play in two EFL classrooms
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-graduação em Letras/Inglês e Literatura CorrespondenteO presente estudo teve como objetivo investigar o fenômeno da Linguagem Lúdica (LL) nas interações em duas salas de aula de Língua Inglesa (LI), pois se acredita que a LL pode facilitar o desenvolvimento dos processos de aprendizagem da LI no ambiente de ensino formal de sala de aula. As idéias sobre o lúdico nos processos de aprendizagem sugeridas por Guy Cook (2000) e diferentes estudos baseados na perspectiva sociocultural (Mitchell e Myles, 1998; Kramsh e Sullivan, 1996; Sullivan, 2000a, 2000b; Broner e Tarone, 2001) deram o embasamento teórico para este estudo. Propôs-se determinar como a LL era caracterizada e classificada e verificar quais as funções as ocorrências de LL estariam exercendo nestas duas salas de aula de LI. Técnicas etnográficas foram aplicadas para que uma mais clara perspectiva do
Functional probiotic products based on fermented wort with Lactobacillus rhamnosus GG and Lactobacillus casei
No full textstatus: Publishe
Identification and spoilage potential of the remaining dominant microbiota on food contact surfaces after cleaning and disinfection in different food industries
No full textAfter cleaning and disinfection (C&D), surface contamination can still be present in the production environment of food companies. Microbiological contamination on cleaned surfaces can be transferred to the manufactured food and consequently lead to foodborne illness and early food spoilage. However, knowledge about the microbiological composition of residual contamination after C&D and the effect of this contamination on food spoilage is lacking in various food sectors. In this study, we identified the remaining dominant microbiota on food contact surfaces after C&D in seven food companies and assessed the spoilage potential of the microbiota under laboratory conditions. The dominant microbiota on surfaces contaminated at >= 10(2) CFU/100 cm(2) after C&D was identified based on 16S rRNA sequences. The ability of these microorganisms to hydrolyze proteins, lipids, and phospholipids, ferment glucose and lactose, produce hydrogen sulfide, and degrade starch and gelatin also was evaluated. Genera that were most abundant among the dominant microbiota on food contact surfaces after C&D were Pseudomonas, Microbacterium, Stenotrophomonas, Staphylococcus, and Streptococcus. Pseudomonas spp. were identified in five of the participating food companies, and 86.8% of the isolates evaluated had spoilage potential in the laboratory tests. Microbacterium and Stenotrophomonas spp. were identified in five and six of the food companies, respectively, and all tested isolates had spoilage potential. This information will be useful for food companies in their quest to characterize surface contamination after C&D, to identify causes of microbiological food contamination and spoilage, and to determine the need for more thorough C&D
Smiling is a Costly Signal of Cooperation Opportunities: Experimental Evidence from a Trust Game
No full textWe test the hypothesis that "genuine" or "convincing" smiling is a costly signal that has evolved to induce cooperation in situations requiring mutual trust. Potential trustees in a trust game made video clips for viewing by potential trusters before the latter decided whether to send them money. Ratings of the genuineness of smiles vary across clips; it is difficult to make convincing smiles to order. We argue that smiling convincingly is costly, because smiles from trustees playing for higher stakes are rated as significantly more convincing, so that rewards appear to induce effort. We show that it induces cooperation: smiles rated as more convincing strongly predict judgments about the trustworthiness of trustees, and willingness to send them money. Finally, we show that it is a honest signal: those smiling convincingly return more money on average to senders. Convincing smiles are to some extent a signal of the intrinsic character of trustees: less honest individuals find smiling convincingly more difficult. They are also informative about the greater amounts that trustees playing for higher stakes have available to share: it is harder to smile convincingly if you have less to offer.
Learning for work from the past, in the present, and into the future?
No full textIn this contribution, the complex interdependencies of the concepts of work and learning and, implicitly, also the concept of knowledge are discussed theoretically from three different but complementary perspectives. The urgency for this exercise lies in the author\u27s belief that learning for work is a topic which cannot be approached in a one-dimensional linear manner. The reason for this lies in the observation that, although in general free will seems to be illusionary in learning for work, we nevertheless acknowledge the individual with their own will, which gives (future) workers some control over changing themselves, their own working life, and the context around their work for the better (Van Dellen & Heidekamp, 2015). The question in this study is whether learning for work is driven by the individual, the actual knowledge aspect of the work, or the more general contextual features of the actual (learning for work) situation. The three different and complementary perspectives that will be discussed concern firstly the idea of the transformative mind (Stetsenko, 2017) using Vygotsky\u27s view of development and learning. The second perspective follows theoretical ideas about transformative learning that concern the complex process of individuals as they develop a more critical world view (Laros, Fuhr, & Taylor, 2017). Finally, the third perspective confronts the learning for work conceptual framework based on Ford\u27s (1992) motivational theory and the philosophical essay about responsibility by Verplaetse (2012) contextualized and operationalized in a study by Van Dellen and Heidekamp (2015). The most practical consequence of all of this theorizing lies in the outcome that learning for work is always something transitional and future-directed. This consequence means a great deal for our ideas about learning and development and the role of education, training, and development both vocationally and professionally. The article ends with a discussion of these consequences
