Streptococcus macedonicus ACA-DC 198 produces the lantibiotic, macedocin, at temperature and pH conditions that prevail during cheese manufacture

Streptococcus macedonicus ACA-DC 198, a natural cheese isolate, produces the anticlostridial bacteriocin, macedocin. Bacteriocin activity was detected from the mid-exponential growth phase and remained constant during the stationary phase. A secondary model was setup to describe the influence of temperature (20-45 degrees C) and pH (5.1-6.9) on cell growth of and bacteriocin production by S. macedonicus ACA-DC 198 during in vitro laboratory fermentations. The optimum temperature for bacteriocin production (20-25 degrees C) was markedly lower than the optimum growth temperature (42.3 degrees C). In contrast, the specific macedocin production was maximal around pH 6.0, whereas growth was optimal at pH 6.4. Consequently, the maximum bacteriocin activity was reached between pH 6.0 and 6.5.     

Local Knowledge Spillovers and Development: An Exploration of the Software Cluster in Uruguay

The paper contributes to the understanding of the nature of local knowledge spillovers and their importance for innovation in clusters in developing countries. Using detailed primary data about a cluster of software firms in Montevideo, Uruguay, the paper finds plenty of evidence of the existence of pure unintentional knowledge spillovers. In addition, it supports previous theoretical studies that have contended that there are also many knowledge flows that are to some degree produced purposively by local parties—these flows can be placed somewhere in between pure spillovers and pure market transactions. While the respondents themselves place most value on knowledge flows that are more or less purposively co-produced with customer transactions, a more objective statistical analysis shows that good product/service-innovation performance is associated with intensive use of flows with more pronounced spillover characteristics. The respondents possibly underrate the latter because of their invisibility and spontaneous nature. Heavy use of knowledge flows lying close to the market-transaction side of the spectrum is found to be associated with relatively advanced organizational capability, but not with product innovation. Overall, the findings point towards the relevance of cluster-based policies to promote innovation in a less developed country context. Various policy measures to stimulate the local circulation of knowledge are suggested.     

Functional properties of novel protective lactic acid bacteria and application in raw chicken meat against Listeria monocytogenes and Salmonella enteritidis

In this study 635 lactic acid bacteria of food origin were evaluated for their potential application as protective cultures in foods. A stepwise selection method was used to obtain the most appropriate strains for application as protective cultures in chicken meat. Specifically, all strains were examined for antimicrobial activity against various Gram positive and Gram negative pathogenic and spoilage bacteria. Strains exhibiting anti-bacterial activity were subsequently examined for survival in simulated food processing and gastrointestinal tract conditions, such as high temperatures, low pH, starvation and the presence of NaCl and bile salts. Selected strains where then examined for basic safety properties such as antibiotic resistance and haemolytic potential, while their antimicrobial activity was further investigated by PCR screening for possession of known bacteriocin genes. Two chosen strains were then applied on raw chicken meat to evaluate their protective ability against two common food pathogens, Listeria monocytogenes and Salmonella enteritidis, but also to identify potential spoilage effects by the application of the protective cultures on the food matrix. Antimicrobial activity in vitro was evident against Gram positive indicators, mainly Listeria and Brochothrix spp., while no antibacterial activity was obtained against any of the Gram negative bacteria tested. The antimicrobial activity was of a proteinaceous nature while strains with anti-listerial activity were found to possess one or more bacteriocin genes, mainly enterocins. Strains generally exhibited sensitivity to pH 2.0, but good survival at 45 °C, in the presence of bile salts and NaCl as well as during starvation, while variable survival rates were obtained at 55 °C. None of the strains was found to be haemolytic while variable antibiotic resistance profiles were obtained. Finally, when the selected strains Enterococcus faecium PCD71 and Lactobacillus fermentum ACA-DC179 were applied as protective cultures in chicken meat against L. monocytogenes and S. enteritidis respectively, a significantly reduced growth of these pathogenic bacteria was observed. In addition, these two strains did not appear to have any detrimental effect on biochemical parameters related to spoilage of the chicken meat.     

Selection of potential probiotic lactic acid bacteria from fermented olives by in vitro tests

The present study aims to evaluate the probiotic potential of lactic acid bacteria (LAB) isolated from naturally fermented olives and select candidates to be used as probiotic starters for the improvement of the traditional fermentation process and the production of newly added value functional foods. Seventy one (71) lactic acid bacterial strains (17 Leuconostoc mesenteroides, 1 Ln. pseudomesenteroides, 13 Lactobacillus plantarum, 37 Lb. pentosus, 1 Lb. paraplantarum, and 2 Lb. paracasei subsp. paracasei) isolated from table olives were screened for their probiotic potential. Lb. rhamnosus GG and Lb. casei Shirota were used as reference strains. The in vitro tests included survival in simulated gastrointestinal tract conditions, antimicrobial activity (against Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli O157:H7), Caco-2 surface adhesion, resistance to 9 antibiotics and haemolytic activity. Three (3) Lb. pentosus, 4 Lb. plantarum and 2 Lb. paracasei subsp. paracasei strains demonstrated the highest final population (>8 log cfu/ml) after 3 h of exposure at low pH. The majority of the tested strains were resistant to bile salts even after 4 h of exposure, while 5 Lb. plantarum and 7 Lb. pentosus strains exhibited partial bile salt hydrolase activity. None of the strains inhibited the growth of the pathogens tested. Variable efficiency to adhere to Caco-2 cells was observed. This was the same regarding strains' susceptibility towards different antibiotics. None of the strains exhibited β-haemolytic activity. As a whole, 4 strains of Lb. pentosus, 3 strains of Lb. plantarum and 2 strains of Lb. paracasei subsp. paracasei were found to possess desirable in vitro probiotic properties similar to or even better than the reference probiotic strains Lb. casei Shirota and Lb. rhamnosus GG. These strains are good candidates for further investigation both with in vivo studies to elucidate their potential health benefits and in olive fermentation processes to assess their technological performance as novel probiotic starters.     

Evaluating user experience of adaptive digital educational games with Activity Theory

Adaptive digital educational games (DEGs) providing players with relevant interventions can enhance gameplay experience. This advance in game design, however, renders the user experience (UX) evaluation of DEGs even more challenging. To tackle this challenge, we developed a four-dimension evaluation framework (i.e., gaming experience, learning experience, adaptivity, and usability) and applied it to an empirical study with a DEG on teaching geography. Mixed-method approaches were adopted to collect data with 16 boys aged 10–11. Specifically, a so-called Dyadic User Experience Tests (DUxT) was employed; participants were paired up to assume different roles during gameplay. Learning efficacy was evaluated with a pre-post intervention measurement using a domain-specific questionnaire. Learning experience, gaming experiences and usability were evaluated with intensive in situ observations and interviews guided by a multidimensional scheme; content analysis of these transcribed audio data was supplemented by video analysis. Effectiveness of adaptivity algorithms was planned to be evaluated with automatic logfiles, which, unfortunately, could not be realised due to some technical problem. Nonetheless, the user-based data could offer some insights into this issue. Furthermore, we attempted to bridge the existing gap in UX research – the lack of theoretical frameworks in understanding user experience – by adopting Engeström's (1987) extended framework of Activity Theory (AT) that provides contextual information essential for understanding contradictions and breakdowns observed in the interactions between the game players. The dyadic gameplay setting allows us to explore the issue of group UX. Implications for further applications of the AT framework in the UX research, especially the interplay between evaluation and redesign (i.e., downstream utility of UX evaluation methods), are discussed.     

The flavone,flavonol and flavan-3-ol content of the Greek traditional diet

Flavonoids are an important category of plant antioxidants and evidence is accumulating on their favorable effects against the development of heart disease and certain forms of cancer. We analytically determined the flavonol (quercetin, kaempferol, myricetin, isorhamnetin), flavone (luteolin, apigenin) and flavan-3-ol (catechin, epicatechin, epigallocatechin, epigallocatechin gallate, epicatechin gallate) content of a weekly menu representative of the Greek traditional diet. The overall daily average content was found 79.01 mg of which flavonols contribute 47% (37.17 mg/day), flavan-3-ols 40% (31.67 mg/day) and flavones 13% (10.17 mg/day). The levels of agreement between the analytical results and the respective theoretical flavonoid calculations conducted previously on the same weekly menu ranged widely, indicating that caution should be taken when calculated flavonoid values are to be used in epidemiological studies. Compared to northern European and American diets, the traditional Greek diet has a higher flavonoid content, at least with respect to flavones, flavonols and flavan-3-ols.     

Detection of changes in the cellular composition of Salmonella enterica serovar Typhimurium in the presence of antimicrobial compound(s) of Lactobacillus strains using Fourier transform infrared spectroscopy

It was previously established that Lactobacillus fermentum ACA-DC 179, Lactobacillus plantarum ACA-DC 287 and Lactobacillus plantarum ACA-DC 2350 exhibit antimicrobial activity against Salmonella enterica serovar Typhimurium. In order to further investigate the killing effect of these microorganisms against Salmonella cells, we employed Fourier transform infrared spectroscopy (FT-IR). Salmonella cells were incubated with different concentrated lactobacilli supernatants and their FT-IR spectra were recorded. The second derivative transformation of the original spectra revealed changes in spectral regions corresponding to absorptions of major cellular constituents (e.g. cell wall, cell membrane, and proteins of the cell) among the Salmonella cells treated with the supernatants and those treated with the control samples. Principal component analysis of the second derivative transformed spectra showed that the yet unidentified antimicrobial compound(s) produced by the lactobacilli tested clearly interfered with the fatty acids of the cell membrane, as well as the polysaccharides of the cell wall in Salmonella cells, pointing towards a dual killing mode. Our study shed light for the first time in the anti-Salmonella activity of the particular Lactobacillus strains.     

Ex-Ante Optimal Design of Sustainable Phase Change Materials for Latent Heat Storage

Energy consumption for residential heating can be reduced using new insulation solutions in the form of phase change materials (PCMs) integrated within the building structure. This work proposes a framework for the optimal design of PCMs considering operational as well as sustainability aspects at the early stages of the material development process. The proposed framework applies computer-aided molecular design tools and considers a practical simulation model to calculate the functional performance of the PCM, as well as a variety of constraints to impose desirable bounds on the material thermophysical properties and its impact on environment and safety.