Proteolytic activities in Bacillus

Characterization of a soy protein hydrolyzate for the development of a functional ingredient

Argentina is a leading country in biodiesel production from soy. Extruded soy is a low-cost byproduct of the soybean oil industry, from which animal feeds are prepared as well as flour for human consumption. Soy proteins can be isolated from flours and digested with enzymes in order to obtain bioactive fractions. In this work, a commercial soy isolate (PRO-FAM 974) was characterized. Maximal solubility was achieved at a concentration of 90 mg/mL. Protein profiles obtained by SDS-PAGE showed that the isolate was constituted mostly by globulins. Conformational and thermal analyses (differential scanning calorimetry) showed that proteins were almost completely denatured. The isolate was hydrolyzed with a commercially available enzyme (COROLASE 7089). The peptide profile (MALDI-TOF) showed peptides ranging from 800 to 10,000 Daltons. We conclude that the product obtained has the potential to be used as functional ingredient for the development of functional foodstuffs, giving the opportunity to add value to the byproducts of the soybean oil industry.

The bag or the spindle: the cell factory at the time of systems' biology

Genome programs changed our view of bacteria as cell factories, by making them amenable to systematic rational improvement. As a first step, isolated genes (including those of the metagenome), or small gene clusters are improved and expressed in a variety of hosts. New techniques derived from functional genomics (transcriptome, proteome and metabolome studies) now allow users to shift from this single-gene approach to a more integrated view of the cell, where it is more and more considered as a factory. One can expect in the near future that bacteria will be entirely reprogrammed, and perhaps even created de novo from bits and pieces, to constitute man-made cell factories. This will require exploration of the landscape made of neighbourhoods of all the genes in the cell. Present work is already paving the way for that futuristic view of bacteria in industry.

Signal peptide-dependent protein transport in Bacillus subtilis: a genome-based survey of the secretome

One of the most salient features of Bacillus subtilis and related bacilli is their natural capacity to secrete a variety of proteins into their environment, frequently to high concentrations. This has led to the commercial exploitation of bacilli as major "cell factories" for secreted enzymes. The recent sequencing of the genome of B. subtilis has provided major new impulse for analysis of the molecular mechanisms underlying protein secretion by this organism. Most importantly, the genome sequence has allowed predictions about the composition of the secretome, which includes both the pathways for protein transport and the secreted proteins. The present survey of the secretome describes four distinct pathways for protein export from the cytoplasm and approximately 300 proteins with the potential to be exported. By far the largest number of exported proteins are predicted to follow the major "Sec" pathway for protein secretion. In contrast, the twin-arginine translocation "Tat" pathway, a type IV prepilin-like export pathway for competence development, and ATP-binding cassette transporters can be regarded as "special-purpose" pathways, through which only a few proteins are transported. The properties of distinct classes of amino-terminal signal peptides, directing proteins into the various protein transport pathways, as well as the major components of each pathway are discussed. The predictions and comparisons in this review pinpoint important differences as well as similarities between protein transport systems in B. subtilis and other well-studied organisms, such as Escherichia coli and the yeast Saccharomyces cerevisiae. Thus, they may serve as a lead for future research and applications.