Developments in the use ofBacillusspecies for industrial production

Abstract

Bacillus species continue to be dominant bacterial workhorses in microbial fermentations. Bacillus subtilis (natto) is the key microbial participant in the ongoing production of the soya-based traditional natto fermentation, and some Bacillus species are on the Food and Drug Administration's GRAS (generally regarded as safe) list. The capacity of selected Bacillus strains to produce and secrete large quantities (20-25 g/L) of extracellular enzymes has placed them among the most important industrial enzyme producers. The ability of different species to ferment in the acid, neutral, and alkaline pH ranges, combined with the presence of thermophiles in the genus, has lead to the development of a variety of new commercial enzyme products with the desired temperature, pH activity, and stability properties to address a variety of specific applications. Classical mutation and (or) selection techniques, together with advanced cloning and protein engineering strategies, have been exploited to develop these products. Efforts to produce and secrete high yields of foreign recombinant proteins in Bacillus hosts initially appeared to be hampered by the degradation of the products by the host proteases. Recent studies have revealed that the slow folding of heterologous proteins at the membrane-cell wall interface of Gram-positive bacteria renders them vulnerable to attack by wall-associated proteases. In addition, the presence of thiol-disulphide oxidoreductases in B. subtilis may be beneficial in the secretion of disulphide-bond-containing proteins. Such developments from our understanding of the complex protein translocation machinery of Gram-positive bacteria should allow the resolution of current secretion challenges and make Bacillus species preeminent hosts for heterologous protein production. Bacillus strains have also been developed and engineered as industrial producers of nucleotides, the vitamin riboflavin, the flavor agent ribose, and the supplement poly-gamma-glutamic acid. With the recent characterization of the genome of B. subtilis 168 and of some related strains, Bacillus species are poised to become the preferred hosts for the production of many new and improved products as we move through the genomic and proteomic era.

Biodiversity and phylogenetic analysis of culturable bacteria indigenous to Khewra salt mine of Pakistan and their industrial importance

“…Out of seven B. licheniformis strains (BPT -7, 11, 12, 18, 19, 20 and 23) only three (BPT-7, 12, and 20) formed endospores (Table 3). Moreover, out of four strains 18,19,20) (1,10). Due to the ubiquity and capability to survive under adverse conditions, heterotrophic Bacillus strains cannot be considered species of certain specific habitats (1).…”

Heterologous production and secretion of Clostridium perfringens β-toxoid in closely related Gram-positive hosts

“…It was previously shown, that adapting the signal sequence can improve protein secretion (Schallmey et al, 2004). The C. perfringens ␤-toxoid native signal sequence is a consensus Sec-type signal sequence, and in theory compatible with the B. subtilis secretion system (Tjalsma et al, 2000).…”

“…subtilis is able to secrete several proteins up to 20 g l −1 (Schallmey et al, 2004), however it is know that secretion of heterologous proteins in B. subtilis is usually lower (Li et al, 2004). A frequently encountered problem with expression and secretion of heterologous proteins in B. subtilis is the rapid degradation of the secreted protein by extracellular proteases (Wu et al, 2002).…”

“…It has an established record for protein production and secretion and general safety. B. subtilis does not contain endotoxins, has been granted a GRAS status by the FDA, and can secrete proteins up to 20 g l −1 yields (Harwood, 1992;Schallmey et al, 2004). Furthermore, like C. perfringens, B. subtilis is a Gram-positive organism, which increases the chance of success for production of ␤-toxin.…”

Amplification, Sequencing and Cloning of Iranian Native Bacillus subtilis Alpha-amylase Gene in Saccharomyces cerevisiae

“…It is estimated that Bacillus sp. enzymes compromised about 50% of the total global enzyme market (8). Bacillus subtilis, B. stearothermophilus, B. licheniformis and B. amyloliquifaciens are known to be good producers of alpha-amylase (9,10).…”