Single-cell protein: overcoming technological and biological challenges towards improved industrialization.

The commercialization of single-cell protein (SCP) obtained from microbial fermentation in large-scale bioreactors emerged almost 50 years ago, with Pruteen marketed as animal feed in the 1970s and Quorn®, released for human nutrition in 1985. SCP holds great promises to feed the meanwhile doubled world population in a sustainable way, but its application is still limited by price and availability on scale. There is a need to optimize the underlying manufacturing processes with enhanced affordability and productivity.

Flavour by design: food-grade lactic acid bacteria improve the volatile aroma spectrum of oat milk, sunflower seed milk, pea milk, and faba milk towards improved flavour and sensory perception.

Background: The global market of plant-based milk alternatives is continually growing. Flavour and taste have a key impact on consumers' selection of plant-based beverages. Unfortunately, natural plant milks have only limited acceptance.

Co-cultures of Propionibacterium freudenreichii and Bacillus amyloliquefaciens cooperatively upgrade sunflower seed milk to high levels of vitamin B and multiple co-benefits.

Background: Sunflower seeds (Helianthus annuus) display an attractive source for the rapidly increasing market of plant-based human nutrition. Of particular interest are press cakes of the seeds, cheap residuals from sunflower oil manufacturing that offer attractive sustainability and economic benefits. Admittedly, sunflower seed milk, derived therefrom, suffers from limited nutritional value, undesired flavor, and the presence of indigestible sugars.

A novel strategy to simultaneously enhance bioaccessible lipids and antioxidants in hetero/mixotrophic Chlorella vulgaris as functional ingredient.

Microalgae are a promising source of polyunsaturated fatty acids as well as bioactive antioxidant compounds such as carotenoids, phenolics and tocopherols. However, the accumulation of these biomolecules is often promoted by conflicting growth conditions. In this study, a phased bioprocessing strategy was developed to simultaneously enhance the lipid and antioxidant amounts by tailoring nitrogen content in the cultivation medium and applying light stress.

Genome-based selection and application of food-grade microbes for chickpea milk fermentation towards increased L-lysine content, elimination of indigestible sugars, and improved flavour.

Background: Plant-based milk alternatives are more popular than ever, and chickpea-based milks are among the most commercially relevant products. Unfortunately, limited nutritional value because of low levels of the essential amino acid L-lysine, low digestibility and unpleasant taste are challenges that must be addressed to improve product quality and meet consumer expectations.

Results: Using in-silico screening and food safety classifications, 31 strains were selected as potential L-lysine producers from approximately 2,500 potential candidates.

Biochemical and Morphological Characterization of Heterotrophic and Cell Walls.

Microalgae are attractive for the food and cosmetic industries because of their nutrient composition. However, the bioaccessibility and extractability of nutrients in microalgae are limited by the rigid and indigestible cell wall. The goal of this study is to explore the cell wall polysaccharides (CWPSs) composition and morphology in heterotrophic and biomasses during growth.

Biochemical and Nutritional Evaluation of and Biomasses Relevant for Food Application.

Microalgae are a source of potentially healthy and sustainable nutrients. However, the bioaccessibility of these nutrients remains uncertain. In this study, we analyzed the biomass composition of five commercial and strains, and heterotrophically cultivated in our laboratory.

Fermentation of plant-based milk alternatives for improved flavour and nutritional value.

Non-dairy milk alternatives (or milk analogues) are water extracts of plants and have become increasingly popular for human nutrition. Over the years, the global market for these products has become a multi-billion dollar business and will reach a value of approximately 26 billion USD within the next 5 years. Moreover, many consumers demand plant-based milk alternatives for sustainability, health-related, lifestyle and dietary reasons, resulting in an abundance of products based on nuts, seeds or beans.

The key to acetate: metabolic fluxes of acetic acid bacteria under cocoa pulp fermentation-simulating conditions.

Acetic acid bacteria (AAB) play an important role during cocoa fermentation, as their main product, acetate, is a major driver for the development of the desired cocoa flavors. Here, we investigated the specialized metabolism of these bacteria under cocoa pulp fermentation-simulating conditions. A carefully designed combination of parallel 13C isotope labeling experiments allowed the elucidation of intracellular fluxes in the complex environment of cocoa pulp, when lactate and ethanol were included as primary substrates among undefined ingredients.

Systems metabolic engineering of Escherichia coli for production of the antitumor drugs violacein and deoxyviolacein.

Violacein and deoxyviolacein are interesting therapeutics against pathogenic bacteria and viruses as well as tumor cells. In the present work, systems-wide metabolic engineering was applied to target Escherichia coli, a widely accepted recombinant host in pharmaceutical biotechnology, for production of these high-value products. The basic producer, E.

Core fluxome and metafluxome of lactic acid bacteria under simulated cocoa pulp fermentation conditions.

In the present work, simulated cocoa fermentation was investigated at the level of metabolic pathway fluxes (fluxome) of lactic acid bacteria (LAB), which are typically found in the microbial consortium known to convert nutrients from the cocoa pulp into organic acids. A comprehensive (13)C labeling approach allowed to quantify carbon fluxes during simulated cocoa fermentation by (i) parallel (13)C studies with [(13)C6]glucose, [1,2-(13)C2]glucose, and [(13)C6]fructose, respectively, (ii) gas chromatography-mass spectrometry (GC/MS) analysis of secreted acetate and lactate, (iii) stoichiometric profiling, and (iv) isotopomer modeling for flux calculation. The study of several strains of L.

Debottlenecking recombinant protein production in Bacillus megaterium under large-scale conditions--targeted precursor feeding designed from metabolomics.

In the present work the impact of large production scale was investigated for Bacillus megaterium expressing green fluorescent protein (GFP). Specifically designed scale-down studies, mimicking the intermittent and continuous nutrient supply of large- and small-scale processes, were carried out for this purpose. The recombinant strain revealed a 40% reduced GFP yield for the large-scale conditions.

On the origin of the electrostatic surface potential of Aspergillus niger spores in acidic environments.

The electrostatic surface potential of fungal spores is generally regarded as potentially influencing spore aggregation and pellet formation in submerged cultures of filamentous fungi. Spores of Aspergillus niger are typically characterized by negative zeta potentials over a wide range of pH values. In this study, this particular behavior is ascribed to the presence of an extensive melanin coating.

Towards methionine overproduction in Corynebacterium glutamicum--methanethiol and dimethyldisulfide as reduced sulfur sources.

In the present work, methanethiol and dimethyldisulfide were investigated as sulfur source for methionine synthesis in Corynebacterium glutamicum. In silico pathway analysis has predicted a high methionine yield for these reduced compounds provided that they can be utilized. Wild type cells were able to grow on methanethiol and on dimethyldisulfide as sole sulfur source, respectively.

Numerical bias estimation for mass spectrometric mass isotopomer analysis.

Mass spectrometric (MS) isotopomer analysis has become a standard tool for investigating biological systems using stable isotopes. In particular, metabolic flux analysis uses mass isotopomers of metabolic products typically formed from (13)C-labeled substrates to quantitate intracellular pathway fluxes. In the current work, we describe a model-driven method of numerical bias estimation regarding MS isotopomer analysis.

Investigation of the central carbon metabolism of Sorangium cellulosum: metabolic network reconstruction and quantification of pathway fluxes.

In the present work, the metabolic network of primary metabolism of the slow-growing myxobacterium Sorangium cellulosum was reconstructed from the annotated genome sequence of the type strain So ce56. During growth on glucose as the carbon source and asparagine as the nitrogen source, So ce56 showed a very low growth rate of 0.23 d-(1), equivalent to a doubling time of 3 days.

Physiological response of Corynebacterium glutamicum to oxidative stress induced by deletion of the transcriptional repressor McbR.

In the present work the metabolic response of Corynebacterium glutamicum to deletion of the global transcriptional regulator McbR, which controls, e.g. the expression of enzymes of L-methionine and L-cysteine biosynthesis and sulfur assimilation, was studied.

Appropriate sampling for intracellular amino acid analysis in five phylogenetically different yeasts.

Methanol quenching and fast filtration, the two most common sampling protocols in microbial metabolome analysis, were validated for intracellular amino acid analysis in phylogenetically different yeast strains comprising Saccharomyces cerevisiae, Kluyveromyces marxianus, Pichia pastoris, Schizosaccharomyces pombe and Zygosaccharomyces bailii. With only few exceptions for selected amino acids, all yeasts exhibited negligible metabolite leakage during quenching with 60% cold buffered methanol. Slightly higher leakage was observed with increasing methanol content in the quenching solution.

Complete genome sequence of the myxobacterium Sorangium cellulosum.

The genus Sorangium synthesizes approximately half of the secondary metabolites isolated from myxobacteria, including the anti-cancer metabolite epothilone. We report the complete genome sequence of the model Sorangium strain S. cellulosum So ce56, which produces several natural products and has morphological and physiological properties typical of the genus.

Metabolic flux engineering of L-lysine production in Corynebacterium glutamicum--over expression and modification of G6P dehydrogenase.

In the present work, metabolic flux engineering of Corynebacterium glutamicum was carried out to increase lysine production. The strategy focused on engineering of the pentose phosphate pathway (PPP) flux by different genetic modifications. Over expression of the zwf gene, encoding G6P dehydrogenase, in the feedback-deregulated lysine-producing strain C.

Sampling for metabolome analysis of microorganisms.

In the present work we investigated the most commonly applied methods used for sampling of microorganisms in the field of metabolomics in order to unravel potential sources of error previously ignored but of utmost importance for accurate metabolome analysis. To broaden the significance of our study, we investigated different Gram-negative and Gram-positive bacteria, i.e.