Purification and properties of β-amylase produced by bacillus polymyxa

Exploration for Thermostable β-Amylase of a Bacillus sp. Isolated from Compost Soil to Degrade Bacterial Biofilm

In an attempt to explore biofilm degradation using extracellular amylase, a potent amylase-producing bacterium of compost origin, B. subtilis B1U/1, was found to grow suitably in a simple medium of pH 7.5 for 48 h at 37°C under agitation of 140 rpm. This bacillary amylase was recovered by ammonium sulfate precipitation and purified to near homogeneity by membrane filtration and DEAE cellulose column chromatography. The amylase was purified to 4.5-fold with almost 50% yield and 26 kDa of molecular weight. Stable enzyme activity was found in a pH range of 5.2 to 9.0, while 90% residual activity was recorded at 90°C, indicating its thermostable nature. In the presence of 1 mM Fe++ and Ca++, the activity of amylase improved; however, it is inhibited by 1 mM Cu++. In the presence of 5% NaCl concentration, amylase showed 50% residual activity. The end product analysis identified the enzyme as β-amylase, and a crystal violet assay ensured that it can degrade Pseudomonas aeruginosa (78%) and Staphylococcus aureus biofilm efficiently (75%). The experiments carried out with the compost soil isolate were promising not only for biotechnological exploitation due to its pH flexibility during growth but also for high efficiency in the degradation of biofilms, which makes the organism a potent candidate in the fields of food industries and biomedical engineering, where it can be used as a prosthetic and hip joint cleaner. The β-amylase is highly thermostable since it withstands an elevated temperature for a prolonged period with a minimum loss of activity and is also moderately salt and metal tolerant. IMPORTANCE More than 85% of nosocomial infections are due to the development of bacterial biofilms. Recent research proposed that biofilm-like structures are not only visible in autopsies, biopsies, patients with chronic wounds, and exudates in animal models but are also present in biomedical devices, implants, prosthetic valves, urinary catheters, etc. Because complete eradication of biofilm is highly challenging, alternative methods, such as enzymatic damage of extracellular matrix and mechanical removal, are being implemented due to their easy availability, low cost, and high yield. Organisms from compost piles are rich sources of diverse extracellular enzymes with a high level of stability, which makes them able to withstand the different conditions of their environments. Under diverse environmental conditions, the enzymes are active to continue degradation processes, making them potential candidates in waste management, medicine, and the food and agriculture industries.

Microbial amylolytic enzymes

Starch-degrading, amylolytic enzymes are widely distributed among microbes. Several activities are required to hydrolyze starch to its glucose units. These enzymes include alpha-amylase, beta-amylase, glucoamylase, alpha-glucosidase, pullulan-degrading enzymes, exoacting enzymes yielding alpha-type endproducts, and cyclodextrin glycosyltransferase. Properties of these enzymes vary and are somewhat linked to the environmental circumstances of the producing organisms. Features of the enzymes, their action patterns, physicochemical properties, occurrence, genetics, and results obtained from cloning of the genes are described. Among all the amylolytic enzymes, the genetics of alpha-amylase in Bacillus subtilis are best known. Alpha-Amylase production in B. subtilis is regulated by several genetic elements, many of which have synergistic effects. Genes encoding enzymes from all the amylolytic enzyme groups dealt with here have been cloned, and the sequences have been found to contain some highly conserved regions thought to be essential for their action and/or structure. Glucoamylase appears usually in several forms, which seem to be the results of a variety of mechanisms, including heterogeneous glycosylation, limited proteolysis, multiple modes of mRNA splicing, and the presence of several structural genes.

Enzymatic degradation of cell wall and related plant polysaccharides

Polysaccharides such as starch, cellulose and other glucans, pectins, xylans, mannans, and fructans are present as major structural and storage materials in plants. These constituents may be degraded and modified by endogenous enzymes during plant growth and development. In plant pathogenesis by microorganisms, extracellular enzymes secreted by infected strains play a major role in plant tissue degradation and invasion of the host. Many of these polysaccharide-degrading enzymes are also produced by microorganisms widely used in industrial enzyme production. Most commerical enzyme preparations contain an array of secondary activities in addition to the one or two principal components which have standardized activities. In the processing of unpurified carbohydrate materials such as cereals, fruits, and tubers, these secondary enzyme activities offer major potential for improving process efficiency. Use of more defined combinations of industrial polysaccharases should allow final control of existing enzyme processes and should also lead to the development of novel enzymatic applications.

General Biochemical Characterization of Thermostable Extracellular β-Amylase from Clostridium thermosulfurogenes

Clostridium thermosulfurogenes , an anaerobic bacterium which ferments starch into ethanol at 62°C, produced an active extracellular amylase and contained intracellular glucoamylase but not pullulanase activity. The extracellular amylase was purified 2.4-fold, and its general physicochemical and catalytic properties were examined. The extracellular amylase was characterized as a β-amylase (1,4-α- d -glucan maltohydrolase) based on demonstration of exocleavage activity and the production of maltose with a β-anomeric configuration from starch. The β-amylase activity was stable and optimally active at 80 and 75°C, respectively. The pH optimum for activity and the pH stability range was 5.5 to 6 and 3.5 to 6.5, respectively. The apparent [S] 0.5 V and V max for β-amylase activity on starch was 1 mg/ml and 60 U/mg of protein. Similar to described β-amylase, the enzyme was inhibited by p -chloromercuribenzoate, Cu 2+ , and Hg 2+ ; however, α- and β-cyclodextrins were not competitive inhibitors. The β-amylase was active and stable in the presence of air or 10% (vol/vol) ethanol. The β-amylase and glucoamylase activities enabled the organism to actively ferment raw starch in the absence of significant pullulanase or α-amylase activity.

Partial Purification and Characterization of a Thermostable Actinomycete β-Amylase

A thermostable amylase, possibly a β-amylase from Thermoactinomyces sp. no. 2 isolated from soil, is reported. The enzyme was purified 36-fold by acetone precipitation, ion-exchange chromatography, and Sephadex G-200 gel filtration, and the molecular weight was estimated at 31,600. The enzyme was characterized by demonstration of optimum activity at 60°C and pH 7 and by retention of 70% activity at 70°C (30 min). It was stimulated by Mn 2+ and Fe 2+ but strongly inhibited by Hg 2+ . Maltose was the only detectable product of hydrolysis of starches and was quantitatively highest in plantain starch hydrolysate.

Beta-Amylase Production by Bacillus polymyxa on a Corn Steep-Starch-Salts Medium

Bacteria were found that are capable of producing good yields of β-amylase in unrefined media. The culture filtrates are free of α-amylase and isoamylase.