Flour carbohydrate catabolism and metabolite production by sourdough lactic acid bacteria

The aim of this study was to assess the mode of carbohydrate catabolism by lactic acid bacteria isolated from traditional sourdoughs, as well as to study their effect on the metabolites produced. For this purpose, single cultures of the heterofermentative lactic acid bacteria Lactobacillus sanfranciscensis, Lactobacillus brevis, Weissella cibaria, and the homofermentative Lactobacillus paralimentarius and Pediococcus pentosaceus were grown in liquid media containing glucose, fructose, maltose and sucrose, either as a single carbon source or in combination with glucose. Carbon catabolism and the production of metabolites were determined by HPLC analysis. W. cibaria could ferment all carbon sources, L. sanfranciscensis, L. paralimentarius and P. pentosaceus could not ferment sucrose, while L. brevis could only ferment maltose. The presence of glucose did not influence the utilization of fructose and maltose by L. sanfranciscensis, while it repressed the fermentation of fructose, maltose and sucrose by W. cibaria, and fructose and maltose by L. paralimentarius and P. pentosaceus. Moreover, L. sanfranciscensis and L. brevis could obtain extra ATP through the reduction of fructose to mannitol, which favored the production of acetic acid against ethanol. The utilization of fructose as an electron acceptor has a decisive effect on the prevailing of L. sanfranciscensis and L. brevis in spontaneously fermented sourdough and in the scarce appearance of the other lactic acid bacteria studied.     

Engineering stem cell fate with biochemical and biomechanical properties of microcarriers

Microcarriers have been widely used for various biotechnology applications because of their high scale‐up potential, high reproducibility in regulating cellular behavior, and well‐documented compliance with current Good Manufacturing Practices (cGMP). Recently, microcarriers have been emerging as a novel approach for stem cell expansion and differentiation, enabling potential scale‐up of stem cell‐derived products in large bioreactors. This review summarizes recent advances of using microcarriers in mesenchymal stem cell (MSC) and pluripotent stem cell (PSC) cultures. From the reported data, efficient expansion and differentiation of stem cells on microcarriers rely on their ability to modulate cell shape (i.e. round or spreading) and cell organization (i.e. aggregate size). Nonetheless, current screening of microcarriers remains empirical, and accurate understanding of how stem cells interact with microcarriers still remains unknown. This review suggests that accurate characterization of biochemical and biomechanical properties of microcarriers is required to fully exploit their potential in regulating stem cell fate decision. Due to the variety of microcarriers, such detailed analyses should lead to the rational design of application‐specific microcarriers, enabling the exploitation of reproducible effects for large scale biomedical applications. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1354–1366, 2013     

Mitonuclear discordance as a confounding factor in the DNA taxonomy of monogonont rotifers

Discordance between mitochondrial and nuclear phylogenies is being increasingly recognized in animals and may confound DNA‐based taxonomy. This is especially relevant for taxa whose microscopic size often challenges any effort to distinguish between cryptic species without the assistance of molecular data. Regarding mitonuclear discordance, two strikingly contrasting scenarios have been recently demonstrated in the monogonont rotifers of the genus Brachionus. While strict mitonuclear concordance was observed in the marine B. plicatilis species complex, widespread hybridization‐driven mitonuclear discordance was revealed in the freshwater B. calyciflorus species complex. Here, we investigated the frequency of occurrence and the potential drivers of mitonuclear discordance in three additional freshwater monogonont rotifer taxa, and assessed its potential impact on the reliability of DNA taxonomy results based on commonly used single markers. We studied the cryptic species complexes of Keratella cochlearis, Polyarthra dolichoptera and Synchaeta pectinata. Phylogenetic reconstructions were based on the mitochondrial barcoding marker cytochrome c oxidase subunit I gene and the nuclear internal transcribed spacer 1 locus, which currently represent the two most typical genetic markers used in rotifer DNA taxonomy. Species were delimited according to each marker separately using a combination of tree‐based coalescent, distance‐based and allele‐sharing‐based approaches. Mitonuclear discordance was observed in all species complexes with incomplete lineage sorting and unresolved phylogenetic reconstructions recognized as the likely drivers. Evidence from additional sources, such as morphology and ecology, is thus advisable for deciding between often contrasting mitochondrial and nuclear species scenarios in these organisms.     

Pigmented variants of Tolypocladium inflatum in relation to cyclosporin A production

Summary We have isolated four distinct colony types of the fungus Tolypocladium inflatum, the producer of the immunosuppresive agent cyclosporin A: morphologically normal white, red, and orange colonies and morphologically diverse tiny brown colonies. In liquid cultures, white normal and brown colonies developed into yellow broths. The broth of the brown colony had a low final pH and low cyclosporin production, whereas orange and red colonies had dark brown and even black broths with higher final pH and high cyclosporin production. The specific production of cyclosporin A by the red colony was three times that of the white normal colonies. Offprint requests to: S. N. Agathos     

Monogonont rotifers as model systems for the study of micro-evolutionary adaptation and its eco-evolutionary implications

A better understanding of the ability of organisms to adapt to local selection conditions is essential for a better insight in their ecological dynamics. The study of micro-evolutionary adaptation and its eco-evolutionary consequences is challenging for many reasons and the choice of a suitable model organism is particularly important. In this paper, we explain why monogonont rotifers, through their unique combination of traits, are ideal study organisms for this purpose. With a literature review, we demonstrate the capacity of monogonont populations to adapt to a variety of selection conditions (e.g., salinity, food shortage, elemental limitation, and disturbance regimes) within very short-time frames and highlight some potential eco-evolutionary implications. Although monogononts are increasingly used in eco-evolution-oriented studies, their potential is still underappreciated compared to other model organisms. No doubt the high prevalence of cryptic species complexes and the lack of genomic tools form important obstacles that may discourage researchers to work with this group. Here, we argue that none of these difficulties should prevent monogonont rotifers from becoming commonly used model organisms in micro-evolutionary studies and make suggestions for future research.     

Effect of Partial Medium Replacement on Cell Growth and Protein Production for the High-Five™ insect cell line

The potential of spent medium to support the growth and recombinant protein production of High-Five? cells was investigated. Growth in medium consisting of three parts fresh and one part spent medium was comparable to that in fresh medium (maximal specific growth rates of 0.028 and 0.029 h^?1, and maximal cell densities of 4 and 4.5 × 10⁶ cells ml^?1, respectively). Glucose exhaustion coincided with an abrupt decrease of viability. Of 15 amino acids analyzed, not a single one was completely exhausted at the end of the growth phase. Growth in medium consisting of equal parts spent and fresh medium led to lower maximal cell concentration (2.9 × 10⁶ cells ml^?1) with a smoother death phase. Glucose supplementation at the beginning of the culture or at the end of the growth phase did not lead to an increase of either the maximal cell density or the specific growth rate. Infection of High-Five? cells at three different densities (1.4, 2.5 and 4.2 × 10⁶ cells ml^?1) without medium change led to monotonically decreased specific productions for β-galactosidase. Partial (75%) or total medium replacement at the higher infection density restored the specific production at the levels of the intermediate density infection (321, 292 and 389 U.(10⁶ cells)^?1, respectively).     

Diel patterns of zooplankton grazing in a shallow lake

A diel survey of in situ species-specific zooplankton clearancerates (with radioactively labelled Chlorella cells) was conductedin the shallow lake of Cr?teil characterized by small-sizedplanktonic forms (algae<10µm and zooplankton <1.3mm). Experiments were performed every 4h at two depths (1 and4m). Power functions relating individual filtering rates tobody length were established for the three most abundant cladoceransand for calanoids (nauplii being included in this feeding group),for each depth and time. No filtering penodicity was observedin Ceriodaphnia spp., adults and copepodites of Eudiaptomusgracilis and Eurytemora velox, and nauplii. On the contrary,clear nocturnal filtering peaks were obtained for Daphnia spp.and for Diaphanosoma brachyurum, these being more pronouncedfor the larger individuals at 1 m deep. The observed diel periodicitycannot be explained by variations in physico-chemical parametersor food concentration alone. The ecological significance ofthis phenomenon in the polymictic lake of Cr?teil is discussedin the light of previously published data and the hypothesesaccounting for it.