Improving production of hyperthermostable and high maltose-forming alpha-amylase by an extreme thermophile Geobacillus thermoleovorans using response surface methodology and its applications

Production of dehairing protease by Bacillus cereus VITSN04: a model cradle-to-cradle approach for sustainable greener production of leathers

Despite several attempts over decades, process scalability and sustainability remain a challenge to produce an environmental-friendly enzyme to gain industrial attention. In the present study, microbial degradation of chrome shavings (chromium-collagen leather waste) and the resulting collagen hydrolysate for producing the dehairing protease by Bacillus cereus VITSN04 were investigated in a lab-scale fermentor. Scale-up degradation of shavings resulted in higher recovery of collagen hydrolysate (76%) within 72 h compared to shake flasks (68% in 120 h). Earlier achieved medium composition of collagen hydrolysate (12 g L-1) and molasses (15 g L-1) appeared to induce amylase at the high rate, despite the maximal production of protease (203.8 ± 0.18 U mL-1), which was analysed by ANS fluorescence spectroscopy. Optimization of the media containing collagen hydrolysate (12 g L-1) and molasses (5 g L-1) was effective in producing protease (170.6 ± 0.1 U mL-1) and reduced the co-synthesis of amylase (48.2 ± 0.09 U mL-1). The controlled fermentation process by feeding molasses during the exponential growth phase had enhanced the dehairing protease production (∼2.96 fold). The produced protease then partitioned through the biphasic system and showed significant dehairing of goat skins on the pilot scale. Thus, the scalability of the process to produce dehairing enzymes using waste, generated at the site of its use, offers hope for sustainable greener production of leathers.

Current status and applications of genus Geobacillus in the production of industrially important products-a review

The genus Geobacillus is one of the most important genera which mainly comprises gram-positive thermophilic bacterial strains including obligate aerobes, denitrifiers and facultative anaerobes having capability of endospore formation as well. The genus Geobacillus is widely distributed in nature and mostly abundant in extreme locations such as cool soils, hot springs, hydrothermal vents, marine trenches, hay composts and dairy plants. Due to plasticity towards environmental adaptation, the Geobacillus sp. shows remarkable genome diversification and acquired many beneficial properties, which facilitates their exploitation for many biotechnological applications. Many thermophiles are of biotechnological importance and having considerable interest in commercial applications for the production of industrially important products. Recently, due to catabolic versatility especially in the degradation of hemicellulose and starch containing agricultural waste and rapid growth rates, these microorganisms show potential for the production of biofuels, thermostable enzymes and bioremediation. This review mainly summarizes the status of Geobacillus sp. including its notable properties, biotechnological studies and its potential application in the production of industrially important products.

Hydrothermal alkaline conversion of sewage sludge: optimization of process parameters and characterization of humic acid

Sewage sludge (SS) dewatering is a key step in sludge disposal, which plays an important role in reducing sludge volume, facilitating transportation and subsequent treatment. In this paper, a facile hydrothermal-alkaline treatment for SS was proposed, which can be used for sludge dewatering and humic acid (HA) recycling at the same time. Response surface methodology (RSM) was used to determine the optimal conditions, and a mathematical model was established to accurately predict the changes of sludge water content and the extraction rate of HA. Under the optimal conditions of 170 °C/42 min/0.05 (for hydrothermal temperature, hydrothermal time, and mass ratio of KOH to wet sludge, respectively), the water content decreased to 46.7% and the extraction rate of HA (with a purity of 96.2%) was 89.1%. The improvement of the dewatering performance effectively facilitates the subsequent disposal of the sludge. The hydrothermal-alkaline method not only realizes the efficient dehydration of the sludge, but also obtains HA from the sludge extract. The obtained HA has potential economic value in the fields of agriculture, biological medicine, environment, and the like.

Production and characterization of psychrophilic α-amylase from a psychrophilic bacterium, Shewanella sp. ISTPL2

A psychrophilic and halophilic bacterial isolate, Shewanella sp. ISTPL2, procured from the pristine Pangong Lake, Ladakh, Jammu and Kashmir, India, was used for the production and characterization of the psychrophilic and alkalophilic α-amylase enzyme. The α-amylase is a critical enzyme that catalyses the hydrolysis of α-1,4-glycosidic bonds of starch molecules and is predominately utilized in biotechnological applications. The highest enzyme activity of partially purified extracellular α-amylase was 10,064.20 U/mL after 12 h of incubation in a shake flask at pH 6.9 and 10 °C. Moreover, the maximum intracellular α-amylase enzyme activity (259.62 U/mL) was also observed at 6 h of incubation. The extracellular α-amylase was refined to the homogeneity with the specific enzyme activity of 36,690.47 U/mg protein corresponding to 6.87-fold purification. The optimized pH and temperature for the α-amylase were found to be pH 8 and 4 °C, respectively, suggesting its stability at alkaline conditions and low or higher temperatures. The amylase activity was highly activated by Cu2+, Fe2+ and Ca2+, while inhibited by Cd2+, Co2+ and Na2+. As per our knowledge, the current study reports the highest activity of a psychrophilic α-amylase enzyme providing prominent biotechnological potential.

Establishment of a functional system for recombinant production of secreted proteins at 50 °C in the thermophilic Bacillus methanolicus

BACKGROUND

The suitability of bacteria as microbial cell factories is dependent on several factors such as price of feedstock, product range, production yield and ease of downstream processing. The facultative methylotroph Bacillus methanolicus is gaining interest as a thermophilic cell factory for production of value-added products from methanol. The aim of this study was to expand the capabilities of B. methanolicus as a microbial cell factory by establishing a system for secretion of recombinant proteins.

RESULTS

Native and heterologous signal peptides were tested for secretion of α-amylases and proteases, and we have established the use of the thermostable superfolder green fluorescent protein (sfGFP) as a valuable reporter protein in B. methanolicus. We demonstrated functional production and secretion of recombinant proteases, α-amylases and sfGFP in B. methanolicus MGA3 at 50 °C and showed that the choice of signal peptide for optimal secretion efficiency varies between proteins. In addition, we showed that heterologous production and secretion of α-amylase from Geobacillus stearothermophilus enables B. methanolicus to grow in minimal medium with starch as the sole carbon source. An in silico signal peptide library consisting of 169 predicted peptides from B. methanolicus was generated and will be useful for future studies, but was not experimentally investigated any further here.

CONCLUSION

A functional system for recombinant production of secreted proteins at 50 °C has been established in the thermophilic B. methanolicus. In addition, an in silico signal peptide library has been generated, that together with the tools and knowledge presented in this work will be useful for further development of B. methanolicus as a host for recombinant protein production and secretion at 50 °C.

A novel approach of integrated bioprocessing of cane molasses for production of prebiotic and functional bioproducts

In this work, the sugar industry by-product cane molasses was investigated as feedstock for acceptor reactions by dextransucrase from Leuconostoc mesenteroides MTCC 10508, leading to the biosynthesis of oligosaccharides. The starch industry corn fiber residue was used as a source for acceptor molecules, maltose, in the reaction. Production of approximately 124g oligosaccharides (DP3-DP6) per kg of fresh molasses was achieved. Further, cane molasses based medium was demonstrated as a sole carbon source for L. mesenteroides growth and dextransucrase production. d-Fructose released by dextransucrase activity as processing by-product was transformed into the functional monosaccharide with zero caloric value, d-psicose, by inducing its epimerization. Quantitative analysis approximated 37g d-psicose per kg of fresh molasses. Thus, the study established a novel approach of integrated bioprocessing of cane molasses into prebiotic and functional food additives.

Screening, statistical optimized production, and application of β-mannanase from some newly isolated fungi

Eighty-eight fungi isolated from soil and decaying organic matter were screened for mannanolytic activity. Twenty-eight fungi produced extracellular mannanase on locust bean gum as evidenced by zone of hydrolysis produced on mannan agar gel. Six prominent producers, including four Fusarium species namely Fusarium fusarioides NFCCI 3282, Fusarium solani NFCCI 3283, Fusarium equiseti NFCCI 3284, Fusarium moniliforme NFCCI 3287 with Cladosporium cladosporioides NFCCI 3285 and Acrophialophora levis NFCCI 3286 produced the β-mannanase in the range of 84-140 nkat/mL. All these grew well on particulate substrates in solid-state fermentation (SSF), producing relatively higher titers on mannan-rich palm kernel cake (PKC) and copra meal. Two high yielding strains, F. equiseti (1747 nkat/gds) and A. levis (897 nkat/gds) were selected for statistical optimization of mannanase on PKC. Interaction of two critical solid state fermentation parameters, pH and moisture on mannanase production by these two molds was studied by response surface method. Optimized production on PKC resulted in three- to fourfold enhancement in enzyme yield was observed in case of F. equiseti (5945 nkat/gds) and A. levis (4726 nkat/gds). HPLC analysis of mannan hydrolysate indicated that F. equiseti and A. levis mannanase performed efficient hydrolysis of konjac gum (up to 99%) with exclusive mannooligosaccahride (DP of 4) production. A seminative SDS-PAGE revealed that A. levis and F. solani produced three isoforms, F. moniliforme produced two isoforms while F. fusarioides, F. equiseti, and C. cladosporioides produced a single 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.

Suitability of the alkalistable carbonic anhydrase from a polyextremophilic bacterium Aeribacillus pallidus TSHB1 in biomimetic carbon sequestration

Carbonic anhydrase (CA) was produced from the polyextremophilic (halotolerant, moderately thermophilic and alkaliphilic) bacterium Aeribacillus pallidus TSHB1 isolated from water and sediment samples of Choti Anhoni hot spring of Pipariya, Madhya Pradesh (India), is being reported to be suitable for carbon sequestration. Growth and CA production were inhibited at higher CO2 concentration (5-10 %). Under optimized culture variables (tryptone 0.8 %, yeast extract 0.08 %, glucose 1 %, micronutrient solution 1 %, inoculums size 1.10 %, agitation 200 at pH 8, and temperature 55 °C), 3.7-fold higher CA production was attained than that under unoptimized conditions. The zymogram analysis of the partially purified CA revealed an activity band corresponding to 32 kDa. The enzyme is stable in the pH range between 8.0 and 11.0 with T 1/2 of 40, 15, and 8 min at 60, 70, and 80 °C, respectively. The CA of A. pallidus displayed a marked enhancement in the rate of CaCO3 precipitation from aqueous CO2. The CA-aided formation of CaCO3 was 42.5 mg mg(-1) protein. Scanning electron microscopy revealed the formation of rhomboid calcite crystals. This is the first report on the production and applicability of CA from the polyextremophilic A. pallidus in carbon sequestration.

Antiadhesive activity of poly-hydroxy butyrate biopolymer from a marine Brevibacterium casei MSI04 against shrimp pathogenic vibrios

Background

Vibrio pathogens are causative agents of mid-culture outbreaks, and early mortality syndrome and secondary aetiology of most dreadful viral outbreaks in shrimp aquaculture. Among the pathogenic vibrios group, Vibrio alginolyticus and V. harveyi are considered as the most significant ones in the grow-out ponds of giant black tiger shrimp Penaeus monodon in India. Use of antibiotics was banned in many countries due to the emergence of antibiotic-resistant strains and accumulation of residual antibiotics in harvested shrimp. There is an urgent need to consider the use of alternative antibiotics for the control of vibriosis in shrimp aquaculture. Biofilm formation is a pathogenic and/or establishment mechanism of Vibrio spp. This study aims to develop novel safe antibiofilm and/or antiadhesive process using PHB to contain vibrios outbreaks in shrimp aquaculture.

Results

In this study a poly-hydroxy butyrate (PHB) polymer producing bacterium Brevibacterium casei MSI04 was isolated from a marine sponge Dendrilla nigra and production of PHB was optimized under submerged-fermentation (SmF) conditions. The effect of carbon, nitrogen and mineral sources on PHB production and enhanced production of PHB by response surface methods were demonstrated. The maximum PHB accumulation obtained was 6.74 g/L in the optimized media containing 25 g/L starch as carbon source, 96 h of incubation, 35°C and 3% NaCl. The highest antiadhesive activity upto 96% was recorded against V. vulnificus, and V. fischeri, followed by 92% against V. parahaemolyticus and V. alginolyticus and 88% inhibition was recorded against V. harveyi.

Conclusion

In this study, a thermostable biopolymer was chemically characterized as PHB based on ¹HNMR spectra, FT-IR and GC-MS spectra. The NMR spectra revealed that the polymer was an isocratic homopolymer and it also confirmed that the compound was PHB. The antiadhesive activity of PHB was determined in microtitre plate assay and an effective concentration (EC) of PHB (200 μl containing 0.6 mg PHB) was confirmed by confocal laser scanning microscopic analysis of vibrio biofilm on pre-treated glass and polystyrene surfaces. This is a first report on anti-adhesive activity of PHB against prominent vibrio pathogens in shrimp aquaculture.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-014-0114-3) contains supplementary material, which is available to authorized users.

Bread Staling: Updating the View

Staling of bread is cause of significant product waste in the world. We reviewed the literature of the last 10 y with the aim to give an up-to-date overview on processing/storage parameters, antistaling ingredients, sourdough technology, and measurement methods of the staling phenomenon. Many researchers have been focusing their interest on the selection of ingredients able to retard staling, mainly hydrocolloids, waxy wheat flours (WWF), and enzymes, but different efforts have been made to understand the molecular basis of bread staling with the help of various measurement methods. Results obtained confirm the central role of amylopectin retrogradation and water redistribution within the different polymers in determining bread staling, but highlighted also the importance of other flour constituents, such as proteins and nonstarch polysaccharides. Data obtained with thermal, spectroscopy, nuclear magnetic resonance, X-ray crystallography, and colorimetry analysis have pointed out the need to encourage the use of one or more of these techniques in order to better understand the mechanisms of staling. Results so far obtained have provided new insight on bread staling, but the phenomenon has not been fully elucidated so far.

Production of cellulase-free xylanase by the recombinant Bacillus subtilis and its applicability in paper pulp bleaching

A metagenomic xylanase gene (Mxyl) was successfully cloned into shuttle vector pWH1520 and expressed in Bacillus subtilis extracellularly. On induction with xylose, recombinant xylanase secretion commenced after 6 h. Identifying critical variables for recombinant xylanase production by one-variable-at-time approach followed by optimization of the selected variables (xylose, inoculum density, incubation density) by response surface methodology (RSM) led to three-fold enhancement in extracellular xylanase production (119 U mL(-1) ). When the pulp was treated with recombinant xylanase at 80°C and pH 9.0, kappa number of the pulp was reduced with concomitant increase in brightness and 24% reduction in chlorine consumption. This is the first report on the expression of metagenomic xylanase gene in Bacillus subtilis extracellularly and its utility in developing an environment-friendly pulp bleaching process.

Process optimization and production of polyhydroxybutyrate using palm jaggery as economical carbon source by marine sponge-associated Bacillus licheniformis MSBN12

The Polyhydroxybutyrate (PHB) producer, Bacillus licheniformis MSBN12 was isolated from the marine sponge Callyspongia diffusa. The PHB production of B. licheniformis MSBN12 was optimized using a four-factor Box-Behnken design to find the interactive effects of variables such as palm jaggery, wheat bran, seawater, and incubation temperature. The maximum yield of PHB (6.38 g/L) was achieved through response surface methodology-based optimization and the optimized conditions were further used for the batch and fed-batch fermentation. Maximum biomass was reached at 48 and 36 h of incubation with PHB accumulation of 62.91 and 67.16 % (w/w of dry cells) for batch and fed-batch process. The production of PHB under fed-batch process with B. licheniformis MSBN12 was increased threefold over shake flask culture when palm jaggery as sole carbon source. The ¹H NMR data was extrapolated with peaks of the PHB reference standard and confirmed as PHB analog.

Optimization of operating parameters for sludge process reduction under alternating aerobic/oxygen-limited conditions by response surface methodology

Batch tests were employed to estimate the optimal conditions for excess sludge reduction under an alternating aerobic/oxygen-limited environment using response surface methodology. Three key operating parameters, initial mixed liquor suspended solids (initial MLSS), HRT (hydraulic retention time) and reaction temperature (T), were selected, and their interrelationships studied by the Box-Behnken design. The experimental data and ANOVA analysis showed that the coefficient of determination (R(2)) was 0.9956 and the adjR(2) was 0.9912, which demonstrates that the modified model was significant. The optimum conditions were predicted to give a maximal ΔMLSS yield of 226 mg/L at an initial MLSS of 10,021 ± 50 mg/L, an HRT of 9.1h and a reaction temperature of 29°C. The prediction was tested by triplicate experiments, where a ΔMLSS yield of 233 mg/L was achieved under the chosen optimal conditions. This excellent correlation between the predicted and measured values provides confidence in the model.

Application of microbial α-amylase in industry - A review

Amylases are one of the main enzymes used in industry. Such enzymes hydrolyze the starch molecules into polymers composed of glucose units. Amylases have potential application in a wide number of industrial processes such as food, fermentation and pharmaceutical industries. α-Amylases can be obtained from plants, animals and microorganisms. However, enzymes from fungal and bacterial sources have dominated applications in industrial sectors. The production of α-amylase is essential for conversion of starches into oligosaccharides. Starch is an important constituent of the human diet and is a major storage product of many economically important crops such as wheat, rice, maize, tapioca, and potato. Starch-converting enzymes are used in the production of maltodextrin, modified starches, or glucose and fructose syrups. A large number of microbial α-amylases has applications in different industrial sectors such as food, textile, paper and detergent industries. The production of α-amylases has generally been carried out using submerged fermentation, but solid state fermentation systems appear as a promising technology. The properties of each α-amylase such as thermostability, pH profile, pH stability, and Ca-independency are important in the development of fermentation process. This review focuses on the production of bacterial and fungal α-amylases, their distribution, structural-functional aspects, physical and chemical parameters, and the use of these enzymes in industrial applications.

Application of response surface methodology for maximizing dextransucrase production from Leuconostoc mesenteroides NRRL B-640 in a bioreactor

The production of dextransucrase from Leuconostoc mesenteroides NRRL B-640 was investigated using statistical approaches. Plackett-Burman design with six variables, viz. sucrose, yeast extract, K(2)HPO(4), peptone, beef extract, and Tween 80, was used to screen the nutrients that significantly affected the dextransucrase production. 2(4)-Central composite design with four selected variables (sucrose, K(2)HPO(4), yeast extract, and beef extract) was used for response surface methodology (RSM) for optimizing the enzyme production. The culture was grown under flask culture with 100 ml optimized medium containing 30 g/l sucrose, 18.5 g/l yeast extract, 15.3 g/l K(2)HPO(4), and 5 g/l beef extract at 25 degrees C and shaking at 200 rpm gave dextransucrase with specific activity of 0.68 U/mg. Whereas the same optimized medium in a 3.0-l bioreactor (1.4 l working volume) gave an experimentally determined value of specific activity of 0.70 U/mg, which was in perfect agreement with the predicted value of 0.65 U/mg by the statistical model.

Purification and characterization of a hyperthermostable and high maltogenic alpha-amylase of an extreme thermophile Geobacillus thermoleovorans

The purified alpha-amylase of Geobacillus thermoleovorans had a molecular mass of 26 kDa with a pI of 5.4, and it was optimally active at 100 degrees C and pH 8.0. The T 1/2 of alpha-amylase at 100 degrees C increased from 3.6 to 5.6 h in the presence of cholic acid. The activation energy and temperature quotient (Q 10) of the enzyme were 84.10 kJ/mol and 1.31, respectively. The activity of the enzyme was enhanced strongly by Co2+ and Fe2+; enhanced slightly by Ba2+, Mn2+, Ni2+, and Mg2+; inhibited strongly by Sn2+, Hg2+, and Pb2+, and inhibited slightly by EDTA, phenyl methyl sulfonyl fluoride, N-ethylmaleimide, and dithiothreitol. The enzyme activity was not affected by Ca2+ and ethylene glycol-bis (beta-amino ethyl ether)-N,N,N,N-tetra acetic acid. Among different additives and detergents, polyethylene glycol 8000 and Tween 20, 40, and 80 stabilized the enzyme activity, whereas Triton X-100, glycerol, glycine, dextrin, and sodium dodecyl sulfate inhibited to a varied extent. alpha-Amylase exhibited activity on several starch substrates and their derivatives. The K m and K cat values (soluble starch) were 1.10 mg/ml and 5.9 x 10(3)/min, respectively. The enzyme hydrolyzed raw starch of pearl millet (Pennisetum typhoides) efficiently.

Production of raw starch-saccharifying thermostable and neutral glucoamylase by the thermophilic mold Thermomucor indicae-seudaticae in submerged fermentation

Among physical and nutritional parameters optimized by "one variable at a time" approach, four cultural variables (sucrose, MgSO4 .7H2O, inoculum size, and incubation period) significantly affected glucoamylase production. These variables were, therefore, selected for optimization using response surface methodology. The p-values of the coefficients for linear effect of sucrose and inoculum size were less than 0.0001, suggesting them to be the key experimental variables in glucoamylase production. The enzyme production (34 U/ml) attained under optimized conditions (sucrose, 2%; MgSO4 .7H2O, 0.13%; yeast extract, 0.1%; inoculum size, 5 x 10(6) spores per 50 ml production medium; incubation time, 48 h; temperature, 40 degrees C; and pH 7.0) was comparable with the value predicted by polynomial model (34.2 U/ml). An over all 3.1-fold higher enzyme titers were attained due to response surface optimization. The experimental model was validated by carrying out glucoamylase production in shake flasks of increasing capacity (0.25-2.0 l) and 22-l laboratory bioreactors (stirred tank and airlift), where the enzyme production was sustainable. Furthermore, the fermentation time was reduced from 48 h in shake flasks to 32 h in bioreactors.