Main conclusion The floral nectars were sucrose-dominant; however, nectar protein and amino acid contents differed, indicating that composition of nitrogenous compounds may vary considerably even between closely related plant species, irrespectively of nectary structure. Numerous zoophilous plants attract their pollinators by offering floral nectar; an aqueous solution produced by specialized secretory tissues, known as floral nectaries. Although many papers on nectaries and nectar already exist, there has been a little research into the structure of nectaries and/or nectar production and composition in species belonging to the same genus. To redress this imbalance, we sought, in the present paper, to describe the floral nectary, nectar production, and nectar composition in five nocturnal Oenothera species with respect to their floral visitors. The structure of nectaries was similar for all the species investigated, and comprised the epidermis (with nectarostomata), numerous layers of nectary parenchyma, and subsecretory parenchyma. Anthesis for a single flower was short (ca. 10–12 h), and flowers lasted only one night. The release of floral nectar commenced at the bud stage (approx. 4 h before anthesis) and nectar was available to pollinators until petal closure. Nectar concentration was relatively low (ca. 27%) and the nectar was sucrose-dominant, and composed mainly of sucrose, glucose and fructose. The protein content of the nectar was also relatively low (on average, 0.31 µg ml−1). Nevertheless, a great variety of amino acids, including both protein and non-protein types, was detected in the nectar profile of the investigated taxa. We noted both diurnal and nocturnal generalist, opportunistic floral insect visitors.

Background: Members of the genus Bifidobacterium are anaerobic Gram-positive Actinobacteria, which are natural inhabitants of human and animal gastrointestinal tract. Certain bifidobacteria are frequently used as food additives and probiotic pharmaceuticals, because of their various health-promoting properties. Due to the enormous demand on probiotic bacteria, manufacture of high-quality products containing living microorganisms requires rapid and accurate identification of specific bacteria. Additionally, isolation of new industrial bacteria from various environments may lead to multiple isolations of the same strain, therefore, it is important to apply rapid, low-cost and effective procedures differentiating bifidobacteria at the intra-species level. The identification of new isolates using microbiological and biochemical methods is difficult, but the accurate characterization of isolated strains may be achieved using a polyphasic approach that includes classical phenotypic methods and molecular procedures. However, some of these procedures are time-consuming and cumbersome, particularly when a large group of new isolates is typed, while some other approaches may have too low discriminatory power to distinguish closely related isolates obtained from similar sources.

Enterobacter aerogenes LU2 was isolated from cow rumen and recognized as a potential succinic acid producer in our previous study. Here, we present the first complete genome sequence of this new, wild strain and report its basic genetic features from a biotechnological perspective. The MinION singlemolecule nanopore sequencer supported by the Illumina MiSeq platform yielded a circular 5,062,651 bp chromosome with a GC content of 55% that lacked plasmids. A total of 4,986 genes, including 4,741 protein-coding genes, 22 rRNA-, 86 tRNA-, and 10 ncRNA-encoding genes and 127 pseudogenes, were predicted. The genome features of the studied strain and other Enterobacteriaceae strains were compared. Functional studies on the genome content, metabolic pathways, growth, and carbon transport and utilization were performed. The genomic analysis indicates that succinic acid can be produced by the LU2 strain through the reductive branch of the tricarboxylic acid cycle (TCA) and the glyoxylate pathway. Antibiotic resistance genes were determined, and the potential for bacteriocin production was verified. Furthermore, one intact prophage region of length ~31,9 kb, 47 genomic islands (GIs) and many insertion sequences (ISs) as well as tandem repeats (TRs) were identified. No clustered regularly interspaced short palindromic repeats (CRISPRs) were found. Finally, comparative genome analysis with well-known succinic acid producers was conducted. The genome sequence illustrates that the LU2 strain has several desirable traits, which confirm its potential to be a highly efficient platform for the production of bulk chemicals. Enterobacter aerogenes LU2 is a gram-negative, wild bacterium that was isolated from cow rumen as a part of environmental screening for succinic acid-producing bacteria identification. Succinic acid (SA) plays an important role as a metabolic intermediate in the rumen by increasing propionate production, a crucial energy source for the ruminant 1,2. Anaerobic conditions and the presence of carbon dioxide, methane and trace amounts of hydrogen create an excellent environment for the biosynthesis of succinate by some bacteria existing in the rumen 3. In reports of the U.S. Department of Energy (DOE) from 2004 and 2010, SA was recognized as one of the top 10 most promising C4-building chemical platforms for the production of high-value commodity and specialty chemicals with great industrial potential 2,4. Succinate is widely applied as an additive in food, pharmaceuticals, detergents, solvents, and surfactants as well as in biodegradable polymer production 5,6. Until recently, industrial production of succinate was based on chemical synthesis. However, petroleum-based production of SA from n-butane through maleic anhydrate requires the use of high pressure, high temperature and costly catalysts 7. Therefore, because of the current global trend regarding sustainable development, including the support of green technologies, rational waste biomass management and pollution-reducing standards, the bio-based production of...

Background: Succinic acid (SA), a valuable chemical compound with a broad range of industrial uses, has become a subject of global interest in recent years. The bio-based production of SA by highly efficient microbial producers from renewable feedstock is significantly important, regarding the current trend of sustainable development. Results: In this study, a novel bacterial strain, LU2, was isolated from cow rumen and recognized as an efficient producer of SA from lactose. Proteomic and genetic identifications as well as phylogenetic analysis were performed, and strain LU2 was classified as an Enterobacter aerogenes species. The optimal conditions for SA production were 100 g/L lactose, 10 g/L yeast extract, and 20% inoculum at pH 7.0 and 34 °C. Under these conditions, approximately 51.35 g/L SA with a yield of 53% was produced when batch fermentation was conducted in a 3-L stirred bioreactor. When lactose was replaced with whey permeate, the highest SA concentration of 57.7 g/L was achieved with a yield and total productivity of 62% and 0.34 g/(L*h), respectively. The highest productivity of 0.67 g/(L*h) was observed from 48 to 72 h of batch fermentation, when E. aerogenes LU2 produced 16.23 g/L SA. Conclusions: This study shows that the newly isolated strain E. aerogenes LU2 has great potential as a new biocatalyst for producing SA from whey permeate.

The genus Lactobacillus includes, among others, Lactobacillus casei, Lactobacillus paracasei and Lactobacillus rhamnosus, species that are collectively referred to as the Lactobacillus casei group. Many studies have shown that strains belonging to this group may decrease lactose intolerance, the effects of inflammatory bowel disease, diarrhea, constipation, food allergies and even colon cancer. Moreover, evidences exists of positive effects of these bacteria on mucosal immunity and blood cholesterol level. Because of their beneficial influence on human health, many of them are used as food additives and probiotic pharmaceuticals. It should be stressed that health-promoting properties are not attributed at the species level, but to specific strains. Therefore, procedures are necessary to allow specific identification at each phylogenetic level—genus, species and strain. In this paper we present a practical overview of molecular methods for the identification and differentiation of L. casei bacteria. The research included 30 bacterial strains belonging to three species: L.casei, L. paracasei and L. rhamnosus. Among the tested procedures were genus- and species-specific PCR, multiplex-PCR, Real-Time HRM analysis, RFLP-PCR, rep-PCR, RAPD-PCR, AFLP-PCR, and proteomic methods such as MALDI-TOF MS typing and SDS-PAGE fingerprinting. The obtained results showed that multiplex-PCR and MALDI-TOF MS turned out to be the most useful methods to identify the tested bacteria at the species level. At the strain level, the AFLP-PCR method showed the highest discriminatory power. We hope that the presented results will allow for the easy selection of an appropriate procedure, depending on the experiment conducted and the equipment capabilities of any given laboratory.

The ability of Rhizopus oryzae to produce fumaric acid in the presence of glycerol and/or various monosaccharides as carbon sources was examined for seventeen different strains of this fungi. These strains were tested in shake-flask cultures on media containing glycerol and seven different carbohydrates, including glucose, fructose, galactose, mannose, xylose, arabinose, and rhamnose. An interesting and applicationally useful phenomenon was observed. This work presents a new approach to the conventional microbiological method of producing fumaric acid. In the presence of 40 g/l glycerol as the sole carbon source, fumaric acid production reached 0.16–6.1 g/l after 192 h. When monosaccharides were used as a single carbon source, the maximum fumaric acid concentration was much higher; for example, 19.8 g/l was achieved when 40 g/l xylose was used. In the co-fermentation of xylose (40 g/l) and glycerol (20 g/l), post-culture broth contained approx. 28.0 g/l of fumaric acid with a process yield of 0.90 g/g after 168 h. The production of fumaric acid by Rhizopus oryzae was also increased in the dual presence of glycerol and monosaccharides like fructose, galactose, and mannose. However, results obtained on glucose-glycerol-based medium did not follow this trend, showing instead complete utilization of glucose with significant glycerol consumption, but unexpectedly low final amounts of fumaric acid and process yields. Understanding how Rhizopus oryzae utilize various carbon sources may provide alternative avenues of fumaric acid fermentation.

The newly-isolated strain Enterobacter sp. LU1, which has previously been shown to be an effective producer of succinic acid on glycerol with the addition of lactose, was used for further intensive works aimed at improving the production parameters of the said process. The introduction of an initial stage of gentle culture aeration allowed almost 47 g/L of succinic acid to be obtained after 168 h of incubation, which is almost two times faster than the time previously taken to obtain this amount. Furthermore, the replacement of glycerol with crude glycerin and the replacement of lactose with whey permeate allowed the final concentration of succinic acid to be increased to 54 g/L. Considering the high content of yeast extract (YE) in the culture medium, tests were also performed with a reduced YE content via its partial substitution with urea. Although this substitution led to a deterioration of the kinetic parameters of the production process, using the fed-batch strategy, it allowed a succinic acid concentration of 69 g/L to be obtained in the culture medium, the highest concentration ever achieved using this process. Furthermore, the use of microaerophilic conditions meant that the addition of lactose to the medium was not required, with 37 g/L of succinic acid being produced on crude glycerol alone.

In dichogamous plants, nectar characteristics (i.e. nectar amount and its composition) can differ between sexual phases. In the present study, we investigated the structural organization of the floral nectary, nectar production and carbohydrate composition in the protandrous Chamaenerion angustifolium (L.) Scop. (Onagraceae). The receptacular nectary consisted of an epidermis with numerous nectarostomata, several layers of photosynthetic secretory parenchyma, and subsecretory parenchyma. Nectariferous tissue was not directly vascularized and starch grains were rarely observed in the secretory cells, occurring exclusively in the guard cells of modified stomata. The nectar was released via nectarostomata. The floral nectar was hexose rich (32.8/39.1/28.1% glucose/ fructose/sucrose) and the total concentration was constant throughout the anthesis (47% on average). However, contrasting patterns in nectar amount and carbohydrate composition between the floral sexual phases were observed. On average, female-phased flowers produced 1.4-fold more nectar than male-phased flowers, and although the nectar was sucrose rich during the male phase, it was hexose rich during the female phase, suggesting sucrose hydrolysis.