Purification of the extracellular protease of Bacillus licheniformis and its inhibition by bacitracin

Determination of the Nutritional Value of Diet Containing Bacillus subtilis Hydrolyzed Feather Meal in Adult Dogs

Simple Summary

The production of meat for human consumption produces extra ingredients used in animal nutrition. Feathers, for example, account for about 7% of the chicken’s body weight. When discarded, it presents a potential risk of environmental contamination. Feathers are minimally digested in mammals and are a very rich source of protein. Improved digestibility can be done by thermal processing or by microorganisms. Bacillus subtilis was shown to have great feather-degrading activity In vitro and we produced an amount of microbial hydrolysate to test in dogs. We did some evaluations on the ingredient to measure the effects of the microorganism on feathers. In dogs, a test of total tract digestibility, microbial resistance to the gastrointestinal tract, and fecal characteristics were performed. Bacillus subtilis was less efficient to digest feathers when a higher concentration of feathers was added to the culture. The amino acid profile in feathers has probably changed due to fermentation. Dogs ate the diets quickly, with no refusals. Nutrient and energy total tract digestibility were lower when compared to thermally processed feathers, but Bacillus subtilis was found viable in the feces of dogs that ingested fermented feathers, signaling that Bacillus subtilis is resistant to digestion and may bring some probiotic effect.

Abstract

Feathers are naturally made up of non-digestible proteins. Under thermal processing, total tract digestibility can be partially improved. Furthermore, Bacillus subtilis (Bs) has shown a hydrolytic effect In vitro. Then, a Bs FTC01 was selected to hydrolyze enough feathers to produce a meal, and then test the quality and inclusion in the dog’s diet to measure the apparent total tract digestibility coefficient (ATTDC) in vivo and the microorganism’s ability to survive in the gastrointestinal tract. A basal diet was added with 9.09% hydrolyzed Bs feather meal (HFMBs) or 9.09% thermally hydrolyzed feather meal (HFMT). Nine adult dogs were randomized into two 10-day blocks and fed different diets. Microbial counts were performed on feather meal, diets and feces. The Bs was less effective in digesting the feathers, which reduced the ATTDC of dry matter, crude protein, energy and increased the production of fecal DM, but the fecal score was maintained (p > 0.05). The digestible energy of HFMT and HFMBs was 18,590 J/kg and 9196 J/kg, respectively. Bacillus subtilis showed limitation to digest feather in large scale, but the resistance of Bs to digestion was observed since it grown on feces culture.

Semi-continuous in situ magnetic separation for enhanced extracellular protease production-modeling and experimental validation

In modern biotechnology proteases play a major role as detergent ingredients. Especially the production of extracellular protease by Bacillus species facilitates downstream processing because the protease can be directly harvested from the biosuspension. In situ magnetic separation (ISMS) constitutes an excellent adsorptive method for efficient extracellular protease removal during cultivation. In this work, the impact of semi-continuous ISMS on the overall protease yield has been investigated. Results reveal significant removal of the protease from Bacillus licheniformis cultivations. Bacitracin-functionalized magnetic particles were successfully applied, regenerated and reused up to 30 times. Immediate reproduction of the protease after ISMS proved the biocompatibility of this integrated approach. Six subsequent ISMS steps significantly increased the overall protease yield up to 98% because proteolytic degradation and potential inhibition of the protease in the medium could be minimized. Furthermore, integration of semi-continuous ISMS increased the overall process efficiency due to reduction of the medium consumption. Process simulation revealed a deeper insight into protease production, and was used to optimize ISMS steps to obtain the maximum overall protease yield.

Thiol/disulfide exchange is required for membrane fusion directed by the Newcastle disease virus fusion protein

Newcastle disease virus (NDV), an avian paramyxovirus, initiates infection with attachment of the viral hemagglutinin-neuraminidase (HN) protein to sialic acid-containing receptors, followed by fusion of viral and cell membranes, which is mediated by the fusion (F) protein. Like all class 1 viral fusion proteins, the paramyxovirus F protein is thought to undergo dramatic conformational changes upon activation. How the F protein accomplishes extensive conformational rearrangements is unclear. Since several viral fusion proteins undergo disulfide bond rearrangement during entry, we asked if similar rearrangements occur in NDV proteins during entry. We found that inhibitors of cell surface thiol/disulfide isomerase activity--5'5-dithio-bis(2-nitrobenzoic acid) (DTNB), bacitracin, and anti-protein disulfide isomerase antibody--inhibited cell-cell fusion and virus entry but had no effect on cell viability, glycoprotein surface expression, or HN protein attachment or neuraminidase activities. These inhibitors altered the conformation of surface-expressed F protein, as detected by conformation-sensitive antibodies. Using biotin maleimide (MPB), a reagent that binds to free thiols, free thiols were detected on surface-expressed F protein, but not HN protein. The inhibitors DTNB and bacitracin blocked the detection of these free thiols. Furthermore, MPB binding inhibited cell-cell fusion. Taken together, our results suggest that one or several disulfide bonds in cell surface F protein are reduced by the protein disulfide isomerase family of isomerases and that F protein exists as a mixture of oxidized and reduced forms. In the presence of HN protein, only the reduced form may proceed to refold into additional intermediates, leading to the fusion of membranes.

Orphan enzymes could be an unexplored reservoir of new drug targets

Despite the immense progress of genomics, and the current availability of several hundreds of thousands of amino acid sequences, >39% of well-defined enzyme activities (as represented by enzyme commission, EC, numbers) are not associated with any sequence. There is an urgent need to explore the 1525 orphan enzymes (enzymes having EC numbers without an associated sequence) to bridge the wide gap that separates knowledge of biochemical function and sequence information. Strikingly, orphan enzymes can even be found among enzymatic activities successfully used as drug targets. Here, knowledge of sequence would help to develop molecular-targeted therapies, suppressing many drug-related side-effects.

Three dimensional structure of the antibiotic bacitracin A complexed to two different subtilisin proteases: novel mode of enzyme inhibition

The three dimensional crystal structures of thermitase-bacitracin (TMTBAC), Savinase- bacitracin (SAVBAC) and Savinase-zinc/bacitracin (SAVBAC/ZN) have been determined by X-ray diffraction to 2.2 angstroms, 2.2 angstroms and 1.95 angstroms resolution, respectively. The multifunctional dodecapeptide bacitracin A secreted by Bacillus licheniformis is well known as an antibiotic against gram-positive bacteria but also as an inhibitor for different proteases. The bacteriocidal activity requires the presence of divalent metal cations such as zinc or nickel. It also could be shown that bacitracin A is bound to subtilisin in the Bacillus licheniformis. This complex is stable throughout the purification by chromatography. Therefore the subtilisin proteases thermitase and Savinase were used for cocrystallization with bacitracin A and zinc/bacitracin A. The complexes are formed from two enzyme molecules and two bacitracin A molecules. All three complexes show the same novel mode of enzyme inhibition. Each bacitracin A chain binds non-covalently to two protease molecules: to the catalytic side of one and to the substrate recognition side of the second protease molecule. In that way the two bacitracin A molecules link two subtilisin molecules together to form a dimer. Despite this common feature we found some important differences in the conformations of bacitracin A in the three complex structures which were analysed and described in detail in this paper. An examination of the solvent structure of the complexes shows water molecules in the region around the bacitracin A molecules are not conserved and play a different role in the stabilization of the bacitracin A conformation.

Characterization of an intracellular serine protease from sporulating cells of Bacillus brevis

Sporulating cells of Bacillus brevis ATCC 9999 produced a high level of an intracellular serine protease when grown in nutrient medium. The protease activity in the crude extracts of this strain appeared at hour 5 (t5) after the end of exponential growth and increased gradually during sporulation, reaching a maximum at t12 to t13. The enzyme isolated in a partially purified state showed a pH optimum between 7.3 and 9.0 and had an apparent molecular weight of about 60,000. The activity was completely inhibited by phenylmethylsulfonyl fluoride, diisopropyl fluorophosphate, EDTA, and ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid. The protease possessed a high activity for azocoll and low activities for azocasein and 14C-labeled hemoglobin. It cleaved the cyclic decapeptide gramicidin S specifically at the peptide linkage between valine and ornithine and hydrolyzed the oxidized insulin B-chain mainly at peptide bonds 4-5 (Glu-His), 6-7 (Leu-CysSO3H), and 15-16 (Leu-Tyr). No catalysis of bond cleavage by the enzyme on a variety of small peptides or esters was detected. Unlike other Bacillus species, B. brevis ATCC 9999 grown in nutrient medium excreted no extracellular proteases.

Direct comparison of the subtilisin-like intracellular protease of Bacillus licheniformis with the homologous enzymes of Bacillus subtilis

Intracellular serine proteases of Bacillus licheniformis and Bacillus subtilis are closely related.

In vitro production of bacitracin by proteolysis of vegetative Bacillus licheniformis cell protein

The action of a sporulation-specific seryl protease on antibiotic-free extracts of Bacillus licheniformis cells yields a peptide that is identified as bacitracin by its biological activity, its spectral properties, and its comigration with genuine bacitracin in both paper and thin-layer chromatography. During proteolysis, a chemical structure is generated with the spectral properties of a delta-2 thiazoline ring. The yield in vitro, 4 microgram of bacitracin per mg of protein, is less than the maximal yield from sporulating cells, 75 microgram of bacitracin per mg of cell protein, but is a linear function of the amount of protein in the reaction system. Approximately 30% of the protein yielding the antibiotic is ribosomal associated, and only 25% of that amount can be removed by washing with 1 M NH4Cl. The substrate protein is a constant fraction of the cell protein throughout exponential growth and very early sporulation stages of culture development.