Model-aided targeted volatile fatty acid production from food waste using a defined co-culture microbial community.

The production of volatile fatty acids (VFA) is gaining momentum due to their central role in the emerging carboxylate platform. Particularly, the production of the longest VFA (from butyrate to caproate) is desired due to their increased economic value and easier downstream processing. While the use of undefined microbial cultures is usually preferred with organic waste streams, the use of defined microbial co-culture processes could tackle some of their drawbacks such as poor control over the process outcome, which often leads to low selectivity for the desired products. However, the extensive experimentation needed to design a co-culture system hinders the use of this technology. In this work, a workflow based on the combined use of mathematical models and wet experimentation is proposed to accelerate the design of novel bioprocesses. In particular, a co-culture consisting of Pediococcus pentosaceus and Megaphaera cerevisiae is used to target the production of high-value odd- and even­carbon VFA. An unstructured kinetic model was developed, calibrated and used to design experiments with the goal of increasing the selectivity for the desired VFA, which were experimentally validated. In the case of even­carbon VFA, the experimental validation showed an increase of 38 % in caproate yield and, in the case of enhanced odd­carbon VFA experiments, the yield of butyrate and caproate diminished by 62 % and 94 %, respectively, while propionate became one of the main end products and valerate yield value increased from 0.007 to 0.085 gvalearte per gconsumed sugar. The workflow followed in this work proved to be a sound tool for bioprocess design due to its capacity to explore and design new experiments in silico in a fast way and ability to quickly adapt to new scenarios.

Atopic asthma after rhinovirus-induced wheezing is associated with DNA methylation change in the SMAD3 gene promoter.

Children with rhinovirus-induced severe early wheezing have an increased risk of developing asthma later in life. The exact molecular mechanisms for this association are still mostly unknown. To identify potential changes in the transcriptional and epigenetic regulation in rhinovirus-associated atopic or nonatopic asthma, we analyzed a cohort of 5-year-old children (n = 45) according to the virus etiology of the first severe wheezing episode at the mean age of 13 months and to 5-year asthma outcome. The development of atopic asthma in children with early rhinovirus-induced wheezing was associated with DNA methylation changes at several genomic sites in chromosomal regions previously linked to asthma. The strongest changes in atopic asthma were detected in the promoter region of SMAD3 gene at chr 15q22.33 and introns of DDO/METTL24 genes at 6q21. These changes were validated to be present also at the average age of 8 years.

Experimental sports drinks with minimal dental erosion effect.

The effects of new experimental sports drinks on dental enamel were studied in vitro using bovine tooth specimens. Profilometric analysis was used to measure the loss of tooth material after immersion of the specimens in the drinks. Thereafter the specimens' surface hardness was measured and scanning electron microphotographs were taken. In addition, 13 commercial sports drinks and experimental drinks containing either citric acid or malic acid were tested for their capacity to dissolve hydroxyapatite in vitro. The erosive effect increased markedly with decreasing pH. The citric acid containing drinks were more erosive than malic acid containing drinks. No erosion was observed with the malic acid containing drink (pH 5.90) but the drink of similar composition containing citric acid caused an erosion 1.3 +/- 1.1 microns deep and a commercial citric acid containing drink caused a lesion 12.3 +/- 4.5 microns deep after 120 min immersion. Softening of enamel was greater in specimens immersed in citric acid than in those immersed in malic acid containing drink. The in vitro hydroxyapatite dissolving effect of the commercial sports drink samples studied (all having a pH under 4.22) was markedly greater (0.48-4.38 mmol/l) than that of the malic acid containing experimental drink (pH 5.50, Ca++ concentration in the supernatant 0.19 mmol/l) and of the similar citric acid containing drink (0.35 mmol/l). The hydroxyapatite dissolving effect of both drinks started to be marked at a pH level of about 5.0 but increased thereafter exponentially with decreasing pH. At pH levels above 4.0 the hydroxyapatite dissolving effect of citric acid containing drinks was greater than that of malic acid containing drinks.

In vitro erosion of bovine enamel caused by acidic drinks and other foodstuffs.

The objective was to compare the erosive effect of some commonly used acidic drinks and milk products on a bovine tooth enamel model system. Conditions were selected to be sufficiently severe to cause erosion. Loss of material after erosion experiments was measured by recording the depth of the surface profile after repeated and prolonged exposure. Changes in the enamel surface were observed by scanning electron microscopy. The reparative mechanisms were studied by immersing test teeth in saliva, with or without (2 ppm) fluoride, after severe demineralization in the test products. According to the t-test for paired means, cola beverages and orange beverages differed from beer, coffee with or without sugar, strawberry yoghurt, buttermilk, and carbonated mineral water at the level P less than 0.01. Each of the last-mentioned test products differed from sports drinks, diet cola beverages and orange juice less significantly. In addition, bathing of teeth in saliva between exposures to the test products did not influence the erosive depth. The results, based on in vitro conditions that ensured erosion, are useful for comparative purposes but cannot be directly extended to the oral cavity under normal use conditions.