Expression and characterization of Bacillus subtilis PY22 α-amylase in Pichia pastoris

Amylases from thermophilic bacteria: structure and function relationship

Amylases hydrolyze starch to diverse products including dextrins and progressively smaller polymers of glucose units. Thermally stable amylases account for nearly 25% of the enzyme market. This review highlights the structural attributes of the α-amylases from thermophilic bacteria. Heterologous expression of amylases in suitable hosts is discussed in detail. Further, specific value maximization approaches, such as protein engineering and immobilization of the amylases are discussed in order to improve its suitability for varied applications on a commercial scale. The review also takes into account of the immobilization of the amylases on nanomaterials to increase the stability and reusability of the enzymes. The function-based metagenomics would provide opportunities for searching amylases with novel characteristics. The review is expected to explore novel amylases for future potential applications.

Pilot-scale production of a highly thermostable α-amylase enzyme from Thermotoga petrophila cloned into E. coli and its application as a desizer in textile industry

In this study, the industrial applications of a highly thermostable α-amylase as a desizer in the textile industry was evaluated. The cloned gene was expressed in different media (ZBM, LB, ZYBM9, and ZB) with IPTG (isopropyl β-d-1-thiogalactopyranoside) used as an inducer. Lactose was also used as an alternate inducer for the T7 promoter system in E. coli. For the large-scale production of the enzyme, different parameters were optimized. The maximum enzyme production was achieved when the volume of medium was 70% of the total volume of fermenter with a 2.0 vvm air supply and 20% dissolved oxygen at a 200 rpm agitation rate. Under all the optimized conditions, the maximum enzyme production was 22.08 U ml⁻¹ min⁻¹ with lactose (200 mM) as an inducer in ZBM medium. The desizing potential of the purified α-amylase enzyme was calculated with different enzyme concentrations (50–300 U ml⁻¹) at different temperatures (50–100 °C), and pHs (4–9) with varying time intervals (30–120 min). The highest desizing activity was found when 150 U ml⁻¹ enzyme units were utilized at 85 °C and at 6.5 pH for 1 h.

Thermostable recombinant α-amylase was produced in a large scale for the desizing of cotton cloth in the textile industry.

Development of thermostable amylase enzyme from Bacillus cereus for potential antibiofilm activity

The marine bacterial strain Bacillus cereus was used to produce amylase enzyme and has excellent alkali-stable and thermostable enzymatic activity. The combined effects of pH, temperature and incubation time on amylase activity were studied using response surface methodology. The amylase enzyme activity was also determined in the presence of various metal ions, chelating agents, detergents and the results showed that the maximum enzyme activity was observed in the presence of calcium chloride (96.1%), EDTA (63.4%) and surf excel (90.6%). The amylase enzyme exhibited excellent antibiofilm activity against marine derived biofilm forming bacteria Pseudomonas aeruginosa and Staphylococcus aureus in microtiter plate assay and congo red assay. Light and confocal laser scanning microscopic (CLSM) analysis were also used to confirm the potential biofilm activity of amylase enzyme. The CLSM analysis showed the inhibition of complete biofilm formation on amylase enzyme treated glass surface. Further in vivo toxicity analysis of amylase enzyme was determined against marine organisms Dioithona rigida and Artemia salina. The results showed that there is no morphological changes were observed due to the minimal toxicity of amylase enzyme. Overall these findings suggested that marine bacterial derived amylase enzyme could be developed as potential antibiofilm agent.

Molecular improvements in microbial α-amylases for enhanced stability and catalytic efficiency

α-Amylases is one of the most important industrial enzyme which contributes to 25% of the industrial enzyme market. Though it is produced by plant, animals and microbial source, those from microbial source seems to have potential applications due to their stability and economic viability. However a large number of α-amylases from different sources have been detailed in the literature, only few numbers of them could withstand the harsh industrial conditions. Thermo-stability, pH tolerance, calcium independency and oxidant stability and starch hydrolyzing efficiency are the crucial qualities for α-amylase in starch based industries. Microbes can be genetically modified and fine tuning can be done for the production of enzymes with desired characteristics for specific applications. This review focuses on the native and recombinant α-amylases from microorganisms, their heterologous production and the recent molecular strategies which help to improve the properties of this industrial enzyme.

Bacterial and Archaeal α-Amylases: Diversity and Amelioration of the Desirable Characteristics for Industrial Applications

Industrial enzyme market has been projected to reach US$ 6.2 billion by 2020. Major reasons for continuous rise in the global sales of microbial enzymes are because of increase in the demand for consumer goods and biofuels. Among major industrial enzymes that find applications in baking, alcohol, detergent, and textile industries are α-amylases. These are produced by a variety of microbes, which randomly cleave α-1,4-glycosidic linkages in starch leading to the formation of limit dextrins. α-Amylases from different microbial sources vary in their properties, thus, suit specific applications. This review focuses on the native and recombinant α-amylases from bacteria and archaea, their production and the advancements in the molecular biology, protein engineering and structural studies, which aid in ameliorating their properties to suit the targeted industrial applications.

Cloning, Purification and Characterization of a Highly Thermostable Amylase Gene of Thermotoga petrophila into Escherichia coli

A putative α-amylase gene of Thermotoga petrophila was cloned and expressed in Escherichia coli BL21 (DE3) using pET-21a (+), as an expression vector. The growth conditions were optimized for maximal expression of the α-amylase using various parameters, such as pH, temperature, time of induction and addition of an inducer. The optimum temperature and pH for the maximum expression of α-amylase were 22 °C and 7.0 pH units, respectively. Purification of the recombinant enzyme was carried out by heat treatment method, followed by ion exchange chromatography with 34.6-fold purification having specific activity of 126.31 U mg(-1) and a recovery of 56.25%. Molecular weight of the purified α-amylase, 70 kDa, was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme was stable at 100 °C temperature and at pH of 7.0. The enzyme activity was increased in the presence of metal ions especially Ca(+2) and decreased in the presence of EDTA indicating that the α-amylase was a metalloenzyme. However, addition of 1% Tween 20, Tween 80 and β-mercaptoethanol constrained the enzyme activity to 87, 96 and 89%, respectively. No considerable effect of organic solvents (ethanol, methanol, isopropanol, acetone and n-butanol) was observed on enzyme activity. With soluble starch as a substrate, the enzyme activity under optimized conditions was 73.8 U mg(-1). The α-amylase enzyme was active to hydrolyse starch forming maltose.

Expression and Characterization of Geobacillus stearothermophilus SR74 Recombinant α-Amylase in Pichia pastoris

Geobacillus stearothermophilus SR74 is a locally isolated thermophilic bacteria producing thermostable and thermoactive α-amylase. Increased production and commercialization of thermostable α-amylase strongly warrant the need of a suitable expression system. In this study, the gene encoding the thermostable α-amylase in G. stearothermophilus SR74 was amplified, sequenced, and subcloned into P. pastoris GS115 strain under the control of a methanol inducible promoter, alcohol oxidase (AOX). Methanol induced recombinant expression and secretion of the protein resulted in high levels of extracellular amylase production. YPTM medium supplemented with methanol (1% v/v) was the best medium and once optimized, the maximum recombinant α-amylase SR74 achieved in shake flask was 28.6 U mL(-1) at 120 h after induction. The recombinant 59 kDa α-amylase SR74 was purified 1.9-fold using affinity chromatography with a product yield of 52.6% and a specific activity of 151.8 U mg(-1). The optimum pH of α-amylase SR74 was 7.0 and the enzyme was stable between pH 6.0-8.0. The purified enzyme was thermostable and thermoactive, exhibiting maximum activity at 65°C with a half-life (t₁/₂) of 88 min at 60°C. In conclusion, thermostable α-amylase SR74 from G. stearothermophilus SR74 would be beneficial for industrial applications, especially in liquefying saccrification.

Impact of gene dosage on the production of lipase from Rhizopus chinensis CCTCC M201021 in Pichia pastoris

In this work, the high-level expression of the lipase r27RCL was achieved by optimization of the lipase gene copy number in the host strain Pichia pastoris. The copy number of the lipase gene proRCL from Rhizopus chinensis CCTCC M201021 was quantified by real-time quantitative polymerase chain reaction and a range of Mut(+) P. pastoris strains carrying one, three, five, and six copies of proRCL were obtained. The maximum lipase activity was achieved at 12,500 U/mL by the five-copy recombinant strain after 96 h of methanol induction in the 7-L fermenter. However, the enzyme activity of the six-copy recombinant strain decreased remarkably. By transcription analysis of proRCL, ERO1, and PDI, it suggested that unfolded protein response seemed to be triggered in the highest copy recombinant strain after 24 h. Thus, elaborate optimization of foreign gene dosage was very important for the high-level expression of foreign proteins in P. pastoris.