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Brazzein is a small sweet-tasting protein found in the red berries of a West African evergreen shrub, Pentadiplandra brazzeana Baillon. Brazzein is highly soluble and stable over a large pH range and at high temperatures, which are characteristics that suggest its use as a natural sweetener. However, Pentadiplandra brazzeana culture is difficult at a large scale, limiting the natural source of brazzein. Heterologous expression of brazzein has been established in numerous systems, including bacteria, yeast, and transgenic plants. Brazzein requires four disulfide bonds to be active in eliciting an intense sweet taste, and the yeast Pichia pastoris appears to be one of the best options for obtaining functional brazzein in high quantities. Employing yeast secretion in the culture medium allows us to obtain fully active brazzein and facilitate purification later. To increase yeast secretion, we compared seven different signal peptides to successfully achieve brazzein secretion using the yeast P. pastoris. The brazzein proteins corresponding to these signal peptides elicited activation of the sweet taste receptor functionally expressed in a cellular assay. Among these tested signal peptides, three resulted in the secretion of brazzein at high levels.

Restriction modification systems (R-M systems), consisting of a restriction endonuclease and a cognate methyltransferase, constitute an effective means of a cell to protect itself from foreign DNA. Identification, characterization, and deletion of the restriction modification system BliMSI, a putative isoschizomer of ClaI from Caryophanon latum, were performed in the wild isolate Bacillus licheniformis MS1. BliMSI was produced as recombinant protein in Escherichia coli, purified, and in vitro analysis demonstrated identical restriction endonuclease activity as for ClaI. A recombinant E. coli strain, expressing the heterologous bliMSIM gene, was constructed and used as the host for in vivo methylation of plasmids prior to their introduction into B. licheniformis to improve transformation efficiencies. The establishment of suicide plasmids in the latter was rendered possible. The subsequent deletion of the restriction endonuclease encoding gene, bliMSIR, caused doubled transformation efficiencies in the respective mutant B. licheniformis MS2 (∆bliMSIR). Along with above in vivo methylation, the establishment of further gene deletions (∆upp, ∆yqfD) was performed. The constructed triple mutant (∆bliMSIR, ∆upp, ∆yqfD) enables rapid genome manipulation, a requirement for genetic engineering of industrially important strains.

The time-to-market challenge is key to success for consumer goods affiliated industries. In recent years, the dairy industry faces a fast and constantly growing demand for enzymatically produced lactose free milk products, mainly driven by emerging markets in South America and Asia. In order to take advantage of this opportunity, we developed a fermentation process for lactase (β-galactosidase) from Kluyveromyces lactis within short time. Here, we describe the process of stepwise increasing the level of control over relevant process parameters during scale-up that established a highly efficient and stable production system. Process development started with evolutionary engineering to generate catabolite-derepressed variants of the K. lactis wild type strain. A high-throughput screening mimicking fed-batch cultivation identified a constitutive lactase overproducer with 260-fold improved activity of 4.4 U per mg dry cell weight when cultivated in glucose minimal medium. During scale-up, process control was progressively increased up to the level of conventional, fully controlled fed-batch cultivations by simulating glucose feed, applying pH- and DOT-sensor technology to small scale, and by the use of a milliliter stirred tank bioreactor. Additionally, process development was assisted by DOE-optimization of the growth medium employing the response surface methodology. This article is protected by copyright. All rights reserved

Enantiomerically pure β‐arylalkyl carboxylic acids are important synthetic intermediates for the preparation of a wide range of compounds with biological and pharmacological activities. A library of 83 enzymes isolated from the metagenome was searched for activity in the hydrolysis of ethyl esters of three racemic phenylalkyl carboxylic acids by a microtiter plate‐based screening using a pH‐indicator assay. Out of these, 20 enzymes were found to be active and were subjected to analytical scale biocatalysis in order to determine their enantioselectivity. The most enantioselective and also enantiocomplementary biocatalysts were then used for preparative scale reactions. Thus, both enantiomers of each of the three phenylalkyl carboxylic acids studied could be obtained in excellent optical purity and high yields.

The title compounds were prepared by a Passerini multi-component reaction and subjected to enzymatic kinetic resolution using 40 enzymes known to be active towards esters of tertiary alcohols. This identified a protease (P1), a thermophilic esterase (PestE) and an esterase of metagenome origin (esterase 8) as the most active and enantioselective biocatalysts. After further optimization of reaction conditions, two compounds were prepared in preparative scale using esterase 8 yielding (+)-1-( tert -butylamino)-2-methyl-1-oxobutyl-2-yl acetate with 93%ee and (−)-1-( tert -butylamino)-2-trifluoro-methyl-1-oxobutyl-2-yl acetate with 47%ee.

International audience

International audience; Brazzein is a small heat- and pH-stable sweet-tasting protein isolated from the West African plant, Pentadiplandra brazzeana. Brazzein combines a highly sweet potency, a long history of human consumption, and a remarkable stability, giving it great potential as a natural sweetener. Due to the difficulties of obtaining brazzein from its natural source, several efforts have been made to express brazzein using various heterologous expression systems. This chapter describes the biochemical, structural, sensory, and physiological properties of brazzein. We will summarize the current knowledge of the structure-activity relationship of brazzein. The biotechnological production of brazzein using various expression systems will also be reviewed. Furthermore, the emerging application of brazzein in the food industry to replace traditional sugars by acting as a natural, good, low-calorie sweetener will be discussed.

Mit zunehmender Leistungsfahigkeit und Brillanz der Hochleistungslaserdioden lassen sich Applikationen adressieren die bisher CO2- und Festkorperlasern vorbehalten waren. Um dies zu befordern fokussiert Bookham seine Entwicklungsanstrengungen nicht nur auf die Erhohung der Ausgangsleistung sondern speziell auf die Steigerung der Brillanz unter Beibehaltung strenger Zuverlassigkeitsanforderungen.

Cyclopentapeptides containing the Arg-Gly-Asp motif have been synthesised using solid-phase assembly of side-chain-protected linear precursors, followed by solution-phase cyclisation. The replacement of the Asp residue by γ-carboxyglutamic acid (Gla) is a novel feature which gives rise to an analogue which inhibits cell adhesion, yet its congeners do not show activity in binding assays with recombinant integrin receptors. NMR techniques support a β/γ-turn conformation in most of the analogues.

Esterases and lipases originating from the metagenome (environmental DNA) were studied for the asymmetric hydrolysis of cis -3,5-diacetoxycyclopent-1-ene 1 . Out of 83 enzymes, 35 were found to be active. Subsequent analytical and laboratory scale reactions identified three enzymes showing excellent (−)-preference and one enzyme with excellent (+)-selectivity exceeding even the performance of recombinant or commercial pig liver esterase, which is known as the best biocatalyst for this compound.

UV laser crosslinking is a potentially powerful tool to investigate transient DNA-protein interactions and binding kinetics in intact cells. As the processes underlying UV laser crosslinking are not fully understood, we have performed a study of the influence of laser pulses with different physical parameters on crosslinking of the progesterone receptor to an oligonucleotide containing a hormone-responsive element. We also studied the influence of the various parameters on the amount of laser-irradiated DNA that can be correctly primer extended as an operational measurement of DNA integrity. A strong influence of pulse intensity and pulse length on the crosslink yield was found, likely due to a change in the 'two photon' processes responsible for crosslinking. The highest efficiency of protein crosslinking to DNA was achieved with femtosecond pulses and should be sufficient to enable use of this technique for in vivo studies.

In healthy human skin host defense molecules such as antimicrobial peptides (AMPs) contribute to skin immune homeostasis. In patients with the congenital disease ectodermal dysplasia (ED) skin integrity is disturbed and as a result patients have recurrent skin infections. The disease is characterized by developmental abnormalities of ectodermal derivatives and absent or reduced sweating. We hypothesized that ED patients have a reduced skin immune defense because of the reduced ability to sweat. Therefore, we performed a label-free quantitative proteome analysis of wash solution of human skin from ED patients or healthy individuals. A clear-cut difference between both cohorts could be observed in cellular processes related to immunity and host defense. In line with the extensive underrepresentation of proteins of the immune system, dermcidin, a sweat-derived AMP, was reduced in its abundance in the skin secretome of ED patients. In contrast, proteins involved in metabolic/catabolic and biosynthetic processes were enriched in the skin secretome of ED patients. In summary, our proteome profiling provides insights into the actual situation of healthy versus diseased skin. The systematic reduction in immune system and defense-related proteins may contribute to the high susceptibility of ED patients to skin infections and altered skin colonization.