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Utilization of algae includes both macroalgae for human consumption dating back to thousands of years, as well as the application of microalgae in health promoting dietary supplements. The autotrophic growth of microalgae is slow, but can be accelerated by optimizing their cultivation conditions. Efficiency optimizations for time and economy should be performed in many parallel experiments. A new high-throughput microalgae cultivation method is presented here, applying 24-low-well microplate with varying illumination, in which the cell growth is followed via evaluation of scanned images. A strain of the genus Nannochloropsis and two Chlorella vulgaris species have been chosen as well described and frequently applied model organisms in order to test the recently developed cultivation system. In these scaled down experiments, the custom design lighting panel was tested by studying the effect of the colour of illumination on cell growth kinetics. RGB LEDs (i.e. light emitting diodes, red: 622 nm, green: 528 nm, and blue: 467 nm) were used individually or together providing red, green, blue, and white colours. While the effect of light’s colour on algae growth was evaluated, also the new system was proven to be suitable for comparing maximal growth rates for different microalgae strains. While the tested two Chlorella isolates reached 1.2–1.4 g l–1 concentrations, the Nannochloropsis strain reached 1.4 g l–1 final cell dry weight, and specific growth rates were observed between 0.58–0.62 day–1.

Open access

In existing processes, the extraction of steviol glycosides from stevia leaves involves many process steps often including extraction by organic solvents. The purpose of the present study was to develop a process for the effective extraction of steviol glycosides, which can provide a concentrated juice exhibiting a high level of recovery with regard to the target compounds, rebaudioside A and stevioside. Pressurized Hot Water Extraction (PHWE) was first optimized with Response Surface Methodology in terms of maximized rebaudioside-A yield and minimized colour components. PHWE was then combined with pressing in a wine-press, resulting higher efficiency for extracting both steviol glycosides in comparison to the reported methods in the literature. Finally, spray drying was applied for both product stabilization and removal of contaminants.

Open access
Developments in Health Sciences
Authors: E Burgettiné Böszörményi, S Németh, A Fodor, K Bélafiné Bakó, D Vozik, Z Csima and I Barcs

Introduction

The prevalence of invasive fungal diseases shows an increasing trend. Due to the frequent but unprofessional usage of antifungal medications, the fungi show decreasing susceptibility towards these agents and this trend may lead to the emergence of resistant pathogens. There is a great need to develop antifungal medications with new mechanisms. One of these options is to apply proteins with natural antifungal effects. The objective was to measure the antifungal efficacy of Xenorhabdus budapestensis in vitro on clinical Candida species (Candida albicans, Candida lusitaniae, Candida krusei, Candida kefyr, Candida tropicalis, and Candida glabrata). Materials and methods: We defined the sensitivity of the Candida species towards antibiotics. We conducted agar diffusion tests with the cleaned biopreparation of X. budapestensis (100%) and its dilutions (80%, 60%, 40%, and 20%). Zones of inhibition were measured after 24, 48, and 96 hr.

Results

Most of the tested Candida species have shown sensitivity to the biopreparation and its 40% dilution. The area of the zones of inhibition did not decrease after several days. The most sensitive species was C. lusitaniae and the least sensitive was C. krusei.

Conclusion

We assume that the proteins produced by X. budapestensis have antifungal effect, as the area of the zones of inhibition did not change.

Open access
Acta Alimentaria
Authors: E. Horvath-Szanics, J. Perjéssy, A. Klupács, K. Takács, A. Nagy, E. Koppány-Szabó, F. Hegyi, E. Németh-Szerdahelyi, M.Y. Du, Z.R. Wang, J.Q. Kan and Zs. Zalán

The increasing consumer demand for less processed and more natural food products – while improving those products’ quality, safety, and shelf-life – has raised the necessity of chemical preservative replacement. Biopreservation refers to extended storage life and enhanced safety of foods using the natural microflora and (or) their antibacterial products. Chitinolytic enzymes are of biotechnological interest, since their substrate, chitin, is a major structural component of the cell wall of fungi, which are the main cause of the spoilage of food and raw plant material. Among the several organisms, many bacteria produce chitinolytic enzymes, however, this behaviour is not general. The chitinase activity of the lactic acid bacteria is scarcely known and studied.

The aim of the present study was to select Lactobacillus strains that have genes encoding chitinase, furthermore, to detect expressed enzymes and to characterise their chitinase activity. Taking into consideration the importance of chitin-bindig proteins (CBPs) in the chitinase activity, CBPs were also examined. Five Lactobacillus strains out of 43 strains from 12 different species were selected by their chitinase coding gene. The presence of the chitinase and chitin-biding protein production were confirmed, however, no chitinolytic activity has been identified.

Open access