Biotechnological Processes in Microbial Amylase Production

Recent trends in production and potential applications of microbial amylases: A comprehensive review

α-amylases are vital biocatalysts that constitute a billion-dollar industry with a substantial and enduring global demand. Amylases hydrolyze the α-1,4-glycosidic linkages in starch polymers to generate maltose and malto-oligosaccharides subunits. Amylases are key enzymes that have promising applications in various industrial processes ranging from pharmaceutical, pulp and paper, textile food industries to bioremediation and biofuel sectors. Microbial enzymes have been widely used in industrial applications owing to their ease of availability, cost-effectiveness and better stability at extreme temperatures and pH. α-amylases derived from distinct microbial origins exhibit diverse characteristics, which make them suitable for specific applications. The routine application of immobilized enzymes has become a standard practice in the production of numerous industrial products across the pharmaceutical, chemical, and food industries. This review details the structural makeup of microbial α-amylase to understand its thermodynamic characteristics, aiming to identify key areas that could be targeted for improving the thermostability, pH tolerance and catalytic activity of α-amylase through various immobilization techniques or specific enzyme engineering methods. Additionally, the review briefly explores the enzyme production strategies, potential sources of α-amylases, and use of cost-effective and sustainable raw materials for enzyme production to obtain α-amylases with unconventional applications in various industrial sectors. Major hurdles, challenges and future prospects involving microbial α-amylases has been briefly discussed by considering its diverse applications in industrial bioprocessing.

Ribosome pausing in amylase producing Bacillus subtilis during long fermentation

BACKGROUND

Ribosome pausing slows down translation and can affect protein synthesis. Improving translation efficiency can therefore be of commercial value. In this study, we investigated whether ribosome pausing occurs during production of the α-amylase AmyM by the industrial production organism Bacillus subtilis under repeated batch fermentation conditions.

RESULTS

We began by assessing our ribosome profiling procedure using the antibiotic mupirocin that blocks translation at isoleucine codons. After achieving single codon resolution for ribosome pausing, we determined the genome wide ribosome pausing sites for B. subtilis at 16 h and 64 h growth under batch fermentation. For the highly expressed α-amylase gene amyM several strong ribosome pausing sites were detected, which remained during the long fermentation despite changes in nutrient availability. These pause sites were neither related to proline or rare codons, nor to secondary protein structures. When surveying the genome, an interesting finding was the presence of strong ribosome pausing sites in several toxins genes. These potential ribosome stall sites may prevent inadvertent activity in the cytosol by means of delayed translation.

CONCLUSIONS

Expression of the α-amylase gene amyM in B. subtilis is accompanied by several ribosome pausing events. Since these sites can neither be predicted based on codon specificity nor on secondary protein structures, we speculate that secondary mRNA structures are responsible for these translation pausing sites. The detailed information of ribosome pausing sites in amyM provide novel information that can be used in future codon optimization studies aimed at improving the production of this amylase by B. subtilis.

Characterization of the microbial communities in paddy soils in Lajas, Puerto Rico using 16S rRNA gene

The microbiota in the paddy soils of the Lajas Agricultural Experimental Station at the University of Puerto Rico (LAES-UPR) plays a crucial role in agricultural ecosystems. Despite being at an experimental station, these soils represent natural environments supporting rice cultivation. Microbial diversity was evaluated during pre-harvest and post-harvest periods.

Antimicrobial therapeutic protein extraction from fruit waste and recent trends in their utilization against infections

Fruits are a very good source of various nutrients that can boost overall human health. In these days, the recovery of therapeutic compounds from different fruit wastes is trending in research, which might not only minimize the waste problem but also encounter a higher demand for various enzymes that could have antimicrobial properties against infectious diseases. The goal of this review is to focus on the recovery of therapeutic enzymes from fruit wastes and its present-day tendency for utilization. Here we discussed different parts of fruit waste, such as pulp, pomace, seed, kernel, peel, etc., that produce therapeutic enzymes like amylase, cellulose, lipase, laccase, pectinase, etc. These bioactive enzymes are present in different parts of fruit and could be used as therapeutics against various infectious diseases. This article provides a thorough knowledge compilation of therapeutic enzyme isolation from fruit waste on a single platform, distinctly informative, and significant review work on the topic that is envisioned to encourage further research ideas in these areas that are still under-explored. This paper explains the various aspects of enzyme isolation from fruit and vegetable waste and their biotherapeutic potential that could provide new insights into the development of biotherapeutics and attract the attention of researchers to enhance translational research magnitude further.

Enhancement of stability and activity of RSD amylase from Paenibacillus lactis OPSA3 for biotechnological applications by covalent immobilization on green silver nanoparticles

The key challenge to the biotechnological applications of amylases is achieving high activity and stability under extreme pH, temperature and often high levels of enzyme denaturants. This study immobilized a novel raw starch-digesting (RSD) amylase from Paenibacillus lactis OPSA3 on glutaraldehyde-activated silver nanoparticles. Effects of time, glutaraldehyde concentration, pH, temperature, and enzyme concentration on immobilization were studied, and the immobilized enzymes were characterized. pH 9.0 was optimum for the enzyme immobilization. The maximum immobilization efficiency of 82.23 ± 7.99 % was achieved at 25 °C for 120 min. After immobilization, the optimum pH and temperature changed from 9.0 to 11.0 and 60 to 70, respectively. Immobilization reduced the amylase's activation energy (KJ/mol) from the initial 58.862 to 45.449 following immobilization. The Km of the amylase decreased after immobilization, while the Vmax increased. The immobilized amylase showed significantly greater storage and thermal stability than the free amylase. At 80, enzyme half-life (min) and D value (min) increased from 12.33 to 179.11 and 40.94 to 594.98, respectively. The immobilized amylase (80-88 %) had more stability to the effects of the studied surfactants than the free enzyme. It also showed improved stability in the presence of commercial detergents compared to the free enzyme. The amylase's enhanced kinetic parameters and stability following successful immobilization on silver nanoparticles indicate its potential for application in the range of biotechnological processes where alkaline- and temperature-stable amylases are employed.

Recent advances in genetic engineering to enhance plant-polysaccharide-degrading enzyme expression in Penicillium oxalicum: A brief review

With the depletion of non-renewable fossil fuels, there has been an increasing emphasis on renewable biomass. Penicillium oxalicum is notable for its exceptional capacity to secrete a diverse array of enzymes that degrade plant polysaccharides into monosaccharides. These valuable monosaccharides can be harnessed in the production of bioethanol and other sustainable forms of energy. By enhancing the production of plant-polysaccharide-degrading enzymes (PPDEs) in P. oxalicum, we can optimize the utilization of plant biomass. This paper presents recent advances in augmenting PPDE expression in P. oxalicum through genetic engineering strategies involving protoplast preparation, transformation, and factors influencing PPDE gene expression.

Approaching Optimal pH Enzyme Prediction with Large Language Models

Enzymes are widely used in biotechnology due to their ability to catalyze chemical reactions: food making, laundry, pharmaceutics, textile, brewing─all these areas benefit from utilizing various enzymes. Proton concentration (pH) is one of the key factors that define the enzyme functioning and efficiency. Usually there is only a narrow range of pH values where the enzyme is active. This is a common problem in biotechnology to design an enzyme with optimal activity in a given pH range. A large part of this task can be completed in silico, by predicting the optimal pH of designed candidates. The success of such computational methods critically depends on the available data. In this study, we developed a language-model-based approach to predict the optimal pH range from the enzyme sequence. We used different splitting strategies based on sequence similarity, protein family annotation, and enzyme classification to validate the robustness of the proposed approach. The derived machine-learning models demonstrated high accuracy across proteins from different protein families and proteins with lower sequence similarities compared with the training set. The proposed method is fast enough for the high-throughput virtual exploration of protein space for the search for sequences with desired optimal pH levels.

Characteristics and kinetics of thermophilic actinomycetes' amylase production on agro-wastes and its application for ethanol fermentation

Thermophilic actinomycetes are commonly found in extreme environments and can thrive and adapt to extreme conditions. These organisms exhibit substantial variation and garnered significant interest due to their remarkable enzymatic activities. This study evaluated the potential of Streptomyces griseorubens NBR14 and Nocardiopsis synnemataformans NBRM9 strains to produce thermo-stable amylase via submerged fermentation using wheat and bean straw. The Box-Behnken design was utilized to determine the optimum parameters for amylase biosynthesis. Subsequently, amylase underwent partial purification and characterization. Furthermore, the obtained hydrolysate was applied for ethanol fermentation using Saccharomyces cerevisiae. The optimal parameters for obtaining the highest amylase activity by NBR14 (7.72 U/mL) and NBRM9 (26.54 U/mL) strains were found to be 40 and 30 °C, pH values of 7, incubation time of 7 days, and substrate concentration (3 and 2 g/100 mL), respectively. The NBR14 and NBRM9 amylase were partially purified, resulting in specific activities of 251.15 and 144.84 U/mg, as well as purification factors of 3.91 and 2.69-fold, respectively. After partial purification, the amylase extracted from NBR14 and NBRM9 showed the highest activity level at pH values of 9 and 7 and temperatures of 50 and 60 °C, respectively. The findings also indicated that the maximum velocity (Vmax) for NBR14 and NBRM9 amylase were 57.80 and 59.88 U/mL, respectively, with Km constants of 1.39 and 1.479 mM. After 48 h, bioethanol was produced at concentrations of 5.95 mg/mL and 9.29 mg/mL from hydrolyzed wheat and bean straw, respectively, through fermentation with S. cerevisiae. Thermophilic actinomycetes and their α-amylase yield demonstrated promising potential for sustainable bio-ethanol production from agro-byproducts.

Hydrogen Production from Enzymatic Pretreated Organic Waste with Thermotoga neapolitana

Biomass from various types of organic waste was tested for possible use in hydrogen production. The composition consisted of lignified samples, green waste, and kitchen scraps such as fruit and vegetable peels and leftover food. For this purpose, the enzymatic pretreatment of organic waste with a combination of five different hydrolytic enzymes (cellulase, amylase, glucoamylase, pectinase and xylase) was investigated to determine its ability to produce hydrogen (H2) with the hydrolyzate produced here. In course, the anaerobic rod-shaped bacterium T. neapolitana was used for H2 production. First, the enzymes were investigated using different substrates in preliminary experiments. Subsequently, hydrolyses were carried out using different types of organic waste. In the hydrolysis carried out here for 48 h, an increase in glucose concentration of 481% was measured for waste loads containing starch, corresponding to a glucose concentration at the end of hydrolysis of 7.5 g·L−1. In the subsequent set fermentation in serum bottles, a H2 yield of 1.26 mmol H2 was obtained in the overhead space when Terrific Broth Medium with glucose and yeast extract (TBGY medium) was used. When hydrolyzed organic waste was used, even a H2 yield of 1.37 mmol could be achieved in the overhead space. In addition, a dedicated reactor system for the anaerobic fermentation of T. neapolitana to produce H2 was developed. The bioreactor developed here can ferment anaerobically with a very low loss of produced gas. Here, after 24 h, a hydrogen concentration of 83% could be measured in the overhead space.

Penicillium chrysogenum: Beyond the penicillin

Almost one century after the Sir Alexander Fleming's fortuitous discovery of penicillin and the identification of the fungal producer as Penicillium notatum, later Penicillium chrysogenum (currently reidentified as Penicillium rubens), the molecular mechanisms behind the massive production of penicillin titers by industrial strains could be considered almost fully characterized. However, this filamentous fungus is not only circumscribed to penicillin, and instead, it seems to be full of surprises, thereby producing important metabolites and providing expanded biotechnological applications. This review, in addition to summarizing the classical role of P. chrysogenum as penicillin producer, highlights its ability to generate an array of additional bioactive secondary metabolites and enzymes, together with the use of this microorganism in relevant biotechnological processes, such as bioremediation, biocontrol, production of bioactive nanoparticles and compounds with pharmaceutical interest, revalorization of agricultural and food-derived wastes or the enhancement of food industrial processes and the agricultural production.

Komagataella phaffii as a Platform for Heterologous Expression of Enzymes Used for Industry

In the 1980s, Escherichia coli was the preferred host for heterologous protein expression owing to its capacity for rapid growth in complex media; well-studied genetics; rapid and direct transformation with foreign DNA; and easily scalable fermentation. Despite the relative ease of use of E. coli for achieving the high expression of many recombinant proteins, for some proteins, e.g., membrane proteins or proteins of eukaryotic origin, this approach can be rather ineffective. Another microorganism long-used and popular as an expression system is baker's yeast, Saccharomyces cerevisiae. In spite of a number of obvious advantages of these yeasts as host cells, there are some limitations on their use as expression systems, for example, inefficient secretion, misfolding, hyperglycosylation, and aberrant proteolytic processing of proteins. Over the past decade, nontraditional yeast species have been adapted to the role of alternative hosts for the production of recombinant proteins, e.g., Komagataella phaffii, Yarrowia lipolytica, and Schizosaccharomyces pombe. These yeast species' several physiological characteristics (that are different from those of S. cerevisiae), such as faster growth on cheap carbon sources and higher secretion capacity, make them practical alternative hosts for biotechnological purposes. Currently, the K. phaffii-based expression system is one of the most popular for the production of heterologous proteins. Along with the low secretion of endogenous proteins, K. phaffii efficiently produces and secretes heterologous proteins in high yields, thereby reducing the cost of purifying the latter. This review will discuss practical approaches and technological solutions for the efficient expression of recombinant proteins in K. phaffii, mainly based on the example of enzymes used for the feed industry.

High-Performance Production of N-Acetyl-d-Neuraminic Acid with Whole Cells of Fast-Growing Vibrio natriegens via a Thermal Strategy

High performance is the core objective that biotechnologists pursue, of which low efficiency, low titer, and side products are the chief obstacles. Here, a thermal strategy is proposed for simultaneously addressing the obstacles of whole-cell catalysis that is widely applied in the food industry. The strategy, by combining fast-growing Vibrio natriegens, thermophilic enzymes, and high-temperature whole-cell catalysis, was successfully applied for the high-performance production of N-acetyl-d-neuraminic acid (Neu5Ac) that plays essential roles in the fields of food (infant formulas), healthcare, and medicine. By using this strategy, we realized the highest Neu5Ac titer and productivity of 126.1 g/L and up to 71.6 g/(L h), respectively, 7.2-fold higher than the productivity of Escherichia coli. The major byproduct acetic acid was also eliminated via quenching complex metabolic side reactions enabled by temperature elevation. This study offers a broadly applicable strategy for producing chemicals relevant to the food industry, providing insights for its future development.

Challenges and prospects of microbial α-amylases for industrial application: a review

α-Amylases are essential biocatalysts representing a billion-dollar market with significant long-term global demand. They have varied applications ranging from detergent, textile, and food sectors such as bakery to, more recently, biofuel industries. Microbial α-amylases have distinct advantages over their plant and animal counterparts owing to generally good activities and better stability at temperature and pH extremes. With the scope of applications expanding, the need for new and improved α-amylases is ever-growing. However, scaling up microbial α-amylase technology from the laboratory to industry for practical applications is impeded by several issues, ranging from mass transfer limitations, low enzyme yields, and energy-intensive product recovery that adds to high production costs. This review highlights the major challenges and prospects for the production of microbial α-amylases, considering the various avenues of industrial bioprocessing such as culture-independent approaches, nutrient optimization, bioreactor operations with design improvements, and product down-streaming approaches towards developing efficient α-amylases with high activity and recyclability. Since the sequence and structure of the enzyme play a crucial role in modulating its functional properties, we have also tried to analyze the structural composition of microbial α-amylase as a guide to its thermodynamic properties to identify the areas that can be targeted for enhancing the catalytic activity and thermostability of the enzyme through varied immobilization or selective enzyme engineering approaches. Also, the utilization of inexpensive and renewable substrates for enzyme production to isolate α-amylases with non-conventional applications has been briefly discussed.

Modifying the amino acids in conformational motion pathway of the α-amylase of Geobacillus stearothermophilus improved its activity and stability

Amino acids along the conformational motion pathway of the enzyme molecule correlated to its flexibility and rigidity. To enhance the enzyme activity and thermal stability, the motion pathway of Geobacillus stearothermophilus α-amylase has been identified and molecularly modified by using the neural relational inference model and deep learning tool. The significant differences in substrate specificity, enzymatic kinetics, optimal temperature, and thermal stability were observed among the mutants with modified amino acids along the pathway. Mutants especially the P44E demonstrated enhanced hydrolytic activity and catalytic efficiency (kcat/KM) than the wild-type enzyme to 95.0% and 93.8% respectively, with the optimum temperature increased to 90°C. This mutation from proline to glutamic acid has increased the number and the radius of the bottleneck of the channels, which might facilitate transporting large starch substrates into the enzyme. The mutation could also optimize the hydrogen bonding network of the catalytic center, and diminish the spatial hindering to the substrate entry and exit from the catalytic center.

Aspergillus clavatus UEM 04: An efficient producer of glucoamylase and α-amylase able to hydrolyze gelatinized and raw starch

The best amylolytic activity production by Aspergillus clavatus UEM 04 occurred in submersed culture, with starch, for 72 h, at 25 °C, and 100 rpm. Exclusion chromatography partially purified two enzymes, which ran as unique bands in SDS-PAGE with approximately 84 kDa. LC-MS/MS identified a glucoamylase (GH15) and an α-amylase (GH13_1) as the predominant proteins and other co-purified proteins. Zn2+, Cu2+, and Mn2+ activated the glucoamylase, and SDS, Zn2+, Fe3+, and Cu2+ inhibited the α-amylase. The α-amylase optimum pH was 6.5. The optimal temperatures for the glucoamylase and α-amylase were 50 °C and 40 °C, and the Tm was 53.1 °C and 56.3 °C, respectively. Both enzymes remained almost fully active for 28-32 h at 40 °C, but the α-amylase thermal stability was calcium-dependent. Furthermore, the glucoamylase and α-amylase KM for starch were 2.95 and 1.0 mg/mL, respectively. Still, the Vmax was 0.28 μmol/min of released glucose for glucoamylase and 0.1 mg/min of consumed starch for α-amylase. Moreover, the glucoamylase showed greater affinity for amylopectin and α-amylase for maltodextrin. Additionally, both enzymes efficiently degraded raw starch. At last, glucose was the main product of glucoamylase, and α-amylase produced mainly maltose from gelatinized soluble starch hydrolysis.

Manipulation of fungal cell wall integrity to improve production of fungal natural products

Fungi, as an important industrial microorganism, play an essential role in the production of natural products (NPs) due to their advantages of utilizing cheap raw materials as substrates and strong protein secretion ability. Although many metabolic engineering strategies have been adopted to enhance the biosynthetic pathway of NPs in fungi, the fungal cell wall as a natural barrier tissue is the final and key step that affects the efficiency of NPs synthesis. To date, many important progresses have been achieved in improving the synthesis of NPs by regulating the cell wall structure of fungi. In this review, we systematically summarize and discuss various strategies for modifying the cell wall structure of fungi to improve the synthesis of NPs. At first, the cell wall structure of different types of fungi is systematically described. Then, strategies to disrupt cell wall integrity (CWI) by regulating the synthesis of cell wall polysaccharides and binding proteins are summarized, which have been applied to improve the synthesis of NPs. In addition, we also summarize the studies on the regulation of CWI-related signaling pathway and the addition of exogenous components for regulating CWI to improve the synthesis of NPs. Finally, we propose the current challenges and essential strategies to usher in an era of more extensive manipulation of fungal CWI to improve the production of fungal NPs.

Isolation and characterization of detergent-compatible amylase-, protease-, lipase-, and cellulase-producing bacteria

Detergent-compatible enzymes are the new trend followed by most in the detergent industry. Cellulases, lipases, proteases, and amylases are among the enzymes frequently used in detergents. Detergent-compatible enzymes can be obtained from many organisms, but the stability, cheapness, and availability of microbial enzymes make them preferable in industrial areas. In the present study, soil samples contaminated with household waste were collected from different regions of Trabzon (Turkey) for amylase-, cellulase-, protease-, and lipase-producing bacteria. A total of 55 bacterial isolates differing in colony morphology were purified from the samples and 25 of the isolates gave positive results in enzyme screening. The enzyme screening experiments revealed that 10 isolates produced amylase, 9 produced lipase, 7 produced cellulase, and 6 produced protease. While 2 isolates showed both protease and lipase activity, for 2 different isolates cellulose and amylase activity were detected together. It was also observed that one isolate, C37PLCA, produced all four enzymes. The morphological, physiological, and biochemical analyses of the bacteria from which we obtained the enzymes were performed and species close to them were determined using 16S rRNA sequences. Based on the results obtained, our enzymes show tremendous promise for the detergent industry.

Maltooligosaccharides: Properties, Production and Applications

Maltooligosaccharides (MOS) are homooligosaccharides that consist of 3-10 glucose molecules linked by α-1,4 glycosidic bonds. As they have physiological functions, they are commonly used as ingredients in nutritional products and functional foods. Many researchers have investigated the potential applications of MOS and their derivatives in the pharmaceutical industry. In this review, we summarized the properties and methods of fabricating MOS and their derivatives, including sulfated and non-sulfated alkylMOS. For preparing MOS, different enzymatic strategies have been proposed by various researchers, using α-amylases, maltooligosaccharide-forming amylases, or glycosyltransferases as effective biocatalysts. Many researchers have focused on using immobilized biocatalysts and downstream processes for MOS production. This review also provides an overview of the current challenges and future trends of MOS production.

Characterization of an Amylolytic Enzyme from Massilia timonae of the GH13_19 Subfamily with Mixed Maltogenic and CGTase Activity

This work reports the characterization of an amylolytic enzyme from the bacteria Massilia timonae CTI-57. A gene encoding this protein was expressed from the pTrcHis2B plasmid in Escherichia coli BL21 Star™ (DE3). The purified protein had 64 kDa, and its modeled structure showed a monomer with the conserved α-amylases structure composed of the domain A with the characteristic (β/α)₈-barrel, the small domain B, and the domain C with an antiparallel beta-sheet. Phylogenetic analysis demonstrated that the expressed protein belongs to the GH13_19 subfamily of glycoside hydrolases. The ions Ca²⁺, Mn²⁺, Na⁺, Mg²⁺, Mo⁶⁺, and K⁺ did activate the purified enzyme, while EDTA and the ions Fe²⁺, Hg²⁺, Zn²⁺, and Cu²⁺ were strong inhibitors. SDS was also a strong inhibitor. The enzyme's optimal pH and temperature were 7.0 and 45 °C, respectively, and its T_m was 62.2 °C. The K_M of the purified enzyme for starch was 13 mg/mL, and the V_max was 0.24 μmol of reducing sugars released per min. The characterized enzyme presented higher specificity for maltodextrin and starch and produced maltose as the main starch hydrolysis product. This is the first characterized maltose-forming amylolytic enzyme from the GH13_19 subfamily. The purified enzyme produced β-cyclodextrin from starch and maltodextrin and could be considered a cyclodextrin glucanotransferase (CGTase). This is the first report of a GH13_19 subfamily enzyme with CGTase activity.

The interaction between the histone acetyltransferase complex Hat1-Hat2 and transcription factor AmyR provides a molecular brake to regulate amylase gene expression

The chromatin structure is generally regulated by chromatin remodelers and histone modifiers, which affect DNA replication, repair, and levels of transcription. The first identified histone acetyltransferase was Hat1/KAT1, which belongs to lysine (K) acetyltransferases. The catalytic subunit Hat1 and the regulatory subunit Hat2 make up the core HAT1 complex. In this study, the results of tandem affinity purification and mass spectrometry and bimolecular fluorescence complementation proved that the Penicillium oxalicum PoHat1-Hat2 is the transcriptional cofactor of the sequence-specific transcription factor PoAmyR, a transcription activator essential for the transcription of amylase gene. ChIP-qPCR results demonstrated that the complex PoHat1-Hat2 is recruited by PoAmyR to the promoters of prominent amylase genes Poamy13A and Poamy15A and performs histone H4 lysine12 acetylation. The result of the yeast two-hybrid test indicated that PoHat2 is the subunit that directly interacts with PoAmyR. PoHat1-Hat2 acts as the molecular brake of the PoAmyR-regulating transcription of amylase genes. A putative model for amylase gene regulation by PoAmyR-Hat2-Hat1 was constructed. Our paper is the first report that the Hat1-Hat2 complex acts as a cofactor for sequence-specific TF to regulate gene expression and explains the mechanism of TF AmyR regulating amylase genes expression.

Activity Assay of Amylase and Xylanase Is Available for Quantitative Assessment of Strain Aging in Cultivated Culinary-Medicinal Morchella Mushrooms (Ascomycotina)

Strain aging has been mainly contributing to the "uncertainty" of Morchella farming. The situation calls for urgent quantitative assessment of strain aging in cultivated Morchella mushrooms. In this paper, systemic senescence of the productive strains of M. eximia, M. importuna, and M. sextelata was achieved through successive subculturing to provide subcultures with different degree of aging for further studies. Then the quantitative assessment of morel strain aging was conducted by activity assay of amylase and xylanase using dinitrosalicylic acid (DNS) method. The results suggested that both activity of amylase and xylanase decreased along with the rise of subculture times. Meanwhile, the correlation between xylanase activity and time of subculturing in the tested morel strains was higher than that of amylase assay. Consequently, assay of amylase and xylanase activity by DNS method can be used in the quantitative assessment of morel strain aging, and assay of xylanase activity is the better alternative. The work will improve the settlement of "uncertainty" in the morel industry and thus be beneficial for stable development of morel farming.

Study on the correlation between microbial communities with physicochemical properties and flavor substances in the Xiasha round of cave-brewed sauce-flavor Baijiu

The Chishui River basin is the main production area of the sauce-flavor Baijiu. Due to the particularity of sauce-flavor Baijiu technology, a large site of workshops needs to be built for brewing and storage. Therefore, used the natural karst caves of Guizhou province to manufacture the sauce-flavor Baijiu, which has enriched the connotation of sauce-flavor Baijiu and saved valuable land resources. In this study, the fermentation grains in the seven stages during the Xiasha round of the cave-brewed sauce-flavor Baijiu (CBSB) were detected using a combination of physicochemical analysis, Headspace solid-phase microextraction gas chromatography-mass detection, and Illumina HiSeq sequencing methods. The results showed Unspecified_Leuconostocaceae, Weissella, Unspecified_Bacillaceae, Saccharomycopsis, Thermomyces, and Unspecified_Phaffomycetaceae were the main bacterial and fungal genera in the stacking fermentation (SF). In the cellar fermentation (CF), the Lactobacillus, Unspecified_Lactobacillaceae, Thermoactinomyces, Saccharomycopsis, Unspecified_Phaffomycetaceae, and Wickerhamomyces were the main bacterial and fungal genera. A total of 72 volatiles were detected in the fermented grains. Linear discriminant analysis Effect Size (LEfSe) identified 23 significantly different volatile metabolites in the fermentation process, including 7 esters, 6 alcohols, 4 acids, 3 phenols, 1 hydrocarbon, and 2 other compounds. Redundancy analysis was used to explore the correlation between dominant microbial genera and physicochemical properties. Starch was the main physicochemical property affecting microbial succession in the SF. Acidity, moisture, and reducing sugar were the main driving factors of microbial succession in the CF. The Pearson correlation coefficient revealed the correlation between dominant microbial genera and significantly different volatile flavor substances. A total of 18 dominant microbial genera were associated with significantly different volatile metabolites, Lactobacillus, Weissella, Wickerhamomyces, and Aspergillus were shown to play crucial roles in metabolite synthesis. On this basis, a metabolic map of the dominant microbial genera was established. This study provides a theoretical basis for the production and quality control of sauce-flavor Baijiu brewed in natural karst caves and lays a foundation for studying the link between flavor formation and microorganisms.

Activity-Based Screening of Soil Samples from Nyingchi, Tibet, for Amylase-Producing Bacteria and Other Multifunctional Enzyme Capacities

Despite the interest in Tibetan soil as a promising source of functional enzymes with potential biotechnological applications, few studies have considered the screening and identification of amylase producing bacteria from Tibetan soil. Amylase has many applications in the food and feed industries, textile and biofuel production, and biomedical engineering. The area of amylase with specific properties is attracting growing attention because of its better application to various industrial conditions. This study aims to screen and identify amylase-producing strains from soil samples collected in Nyingchi, Tibet, and then explore whether the bacterial isolates are superior for unique enzymes. In this paper, a total of 127 amylase producing bacteria were isolated by activity-based screening of six Tibetan soil samples. The 16S rRNA gene survey then identified four major phyla, namely, firmicutes, bacteroidetes, proteobacteria, and actinobacteria, which were differentiated into twelve genera with a dominance of Bacillus (67.72%), followed by Pseudomonas (8.66%). Microbial diversity analysis revealed that the amylase-producing bacterial community of the Kadinggou forest soil sample showed the best variety (the Simpson index was 0.69 and the Shannon index was 0.85). The amylase activity assay of the bacterial isolates showed a mean of 0.66 U/mL at 28°C and pH 5.2. Based on the effect of temperatures and pHs on amylase activity, several bacterial isolates can produce thermophilic (50°C), psychrophilic (10°C), acidophilic (pH 4.2), and alkaliphilic (pH 10.2) amylases. Furthermore, four bacterial isolates were screened for amylase, protease, and esterase activities, which indicated multifunctional enzyme capacities. The present study is expected to contribute to our understanding of Tibetan microbial resources and their potential for scientific research and industrial applications.

Molecular analysis of acid-stable alpha-amylase (asAA) gene in Aspergillus niger using PCR-RFLP

Introduction and Aim: Amylase is an important enzyme with vast applications in various industries such as food and therapeutic industries. Aspergillus niger is commercially engaged in the making of alpha-amylase. Acid-stable alpha -amylase is mostly produced with microorganisms such as Bacillus and Aspergillus. The aim of this research was the molecular investigation of the acid-stable alpha-amylase (alpha-sAA) gene in A. niger.   Materials and Methods: Sixty-three A. niger isolates were evaluated in this study.  PCR method was performed for amplification of a 347 bp DNA band of the alpha-sAA gene.  The Hpa II Restriction endonuclease was used for the digestion of PCR fragments.   Results: A 347 bp DNA fragment was recovered from 49 out of 63 (78%) isolates. After cutting the PCR products with the HpalphaII enzyme, 81.6% of isolates showed the expected band and 18.4% presented different restriction endonuclease patterns.   Conclusion: The results demonstrated the PCR-RFLP technique performed in this research was a valuable tool for analysis of the alpha-sAA gene in A. niger isolates.

Agarase, Amylase and Xylanase from Halomonas meridiana: A Study on Optimization of Coproduction for Biomass Saccharification

Coproduction of multienzymes from single potential microbe has captivated contemplation in industries. Bacterial strain, Halomonas meridiana VITSVRP14, isolated from seaweed was labored to produce amylase, agarase and xylanase conjointly using submerged fermentation. The optimum production conditions clinched by classical optimization were: pH 8; 1.5% inoculum; 24 h incubation, 40 °C; 8% NaCl (sodium chloride); 1% lactose and NaNO3 (sodium nitrate). The preponderant variables (pH, temperature, lactose) and their interaction effect on enzyme production were studied by Plackett-Burman design and Response Surface Methodology (RSM). There were 3.29, 1.81 and 2.08 fold increase in enzyme activity with respect to agarase, amylase and xylanase after optimization against basal medium. After 24 h of enzymatic treatment, the saccharification rates of the coproduced enzyme mixture were 38.96% on rice bran, 49.85% on wheat bran, 61.2% on cassava bagasse and 57.82% on corn cob. Thus, the coproduced enzyme mixture from a bacterium with halotolerance is plausible in pretreated lignocellulose degradation. The ability of this single microbe Halomonas meridiana VITSVRP14, in coproducing agarase, amylase and xylanase give the nod for its application in biomass saccharification by subsiding cost, energy and time involved in the process.

Aspergillus welwitschiae: A Potential amylases Producer

Amylases, glycoside hydrolases widely used in several industrial processes, can be produced by many animals, plants, bacteria, and fungi. Fungal amylases from Aspergillus sp. hold remarkable importance in biotechnological applications for presenting a great catalysis efficiency in a wide range of pH and temperature. The production of amylases is mainly dependent on the genetic background of the species, i.e., Aspergillus strains, and abiotic factors. Among the major producers of amylases are the species of Aspergillus section Nigri, including Aspergillus welwitschiae. In this study, Aspergillus welwitschiae strains were evaluated for their ability to produce extracellular amylases. Among the 24 strains, wild Aspergillus welwitschiae UELAs 15.262 and mutant A. welwitschiae UELAs 15.262/35 strains showed greater potential for amylases production. The A. welwitschiae UELAs 15.262 produced more amylases (8645 U/mg) when compared to A. welwitschiae UELAs 15.262/35 (6666 U/mg). The amylases activity from partially purified crude enzymatic extract of A. welwitschiae UELAs 15.262 strain obtained at pH 5.5, 60 °C, resulted in 1.98-fold (3837 U/mg) increase in enzymatic activity. Likewise, the amylases activity from partially purified crude extract of A. welwitschiae UELAs 15.262/35 obtained at pH 5.0, 60 °C resulted in 2.2-fold (9077 U/mg) increase in amylases activity. The presence of metallic ions (Cu²⁺ and Fe³⁺) also provided an increase of amylases activity for both strains. To our knowledge, this is the first study reporting the ability of Aspergillus welwitschiae strains in order to produce amylases.

A systematic review on potential microbial carbohydrases: current and future perspectives

Various studies have shown that the microbial proteins are often more stable than belongs to other sources like plant and animal origin. Hence, the interest in microbial enzymes has gained much attention due to many potential applications like bioenergy, biofuel production, biobleaching, bioconversion and so on. Additionally, recent trends revealed that the interest in isolating novel microbes from harsh environments have been the main focus of many scientists for various applications. Basically, industrially important enzymes can be categorized into mainly three groups: carbohydrases, proteases, and lipases. Among those, the enzymes especially carbohydrases involved in production of sugars. Carbohydrases include amylases, xylanases, pectinases, cellulases, chitinases, mannases, laccases, ligninases, lactase, glucanase, and glucose oxidase. Thus, here, an approach has been made to highlight five enzymes namely amylase, cellulase, laccase, pectinase, and xylanase from different sources with special emphasis on their properties, mechanism, applications, production optimization, purification, molecular approaches for its enhanced and stable production, and also biotechnological perspectives of its future development. Also, green and sustainable catalytic conversion strategies using nanoparticles of these enzymes have also been discussed. This review will provide insight into the carbohydrases importance and their usefulness that will help to the researchers working in this field.

Orrella daihaiensis sp. nov., a bacterium isolated from Daihai Lake in Inner Mongolia

A novel aerobic, Gram-staining-negative, non-motile, short-rod-shaped strain, designated f23^T, was obtained from Daihai Lake, Inner Mongolia, Republic of China. 16S rRNA gene sequences analysis showed that f23^T belongs to the genus Orrella and is most closely related to Orrella marina H-Z20^T with 98.35% sequence similarity. The strain was oxidase positive, catalase positive and had well growth at pH 6.5-8.5, at temperature 28-40 °C and at 0-4.5% (w/v) NaCl. Colonies incubated at 37 °C on marine 2216 agar for 3 days were white, smooth, transparent, circular and less than 1.0 mm in diameter. The total genome size of f23^T was 2,803,849 bp with a G + C content of 52.79%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain f23^T and O. marina H-Z20^T were 69.62% and 20.5%, which both below the species delineation threshold. Chemotaxonomic analysis showed that C_16:0, cyclo-C_17:0, C_18:0, Sum Feature 3 (C_16:1ω7c and/or C_16:1ω6c) and Sum Feature 8 (C_18:1ω6c and C_18:1ω7c) as the major fatty acids, ubiquinone-8 as the major isoprenoid quinone, phosphatidylethanolamine as the major cellular polar lipids. Based on the polyphasic analysis, f23^T represents a novel species within the genus Orrella, for which the name Orrella daihaiensis sp. nov. is proposed. The type strain is f23^T (= CGMCC 1.18761 ^T = KCTC 82425 ^T).

Improved Production of α-Amylase by Aspergillus terreus in Presence of Oxygen-Vector

n-Dodecane has been investigated as an oxygen-vector for improving α-amylase biosynthesis using the strain Aspergillus terreus. In aerobic microbial cultivation, continuous supply of oxygen is required especially due to its low solubility in the growth medium, in particular at high viscosity, but the limitations of oxygen mass transfer in these systems can be overcome by the addition of water-insoluble compounds which possess a strong affinity for oxygen, namely oxygen-vectors. The use of n-dodecane (as an oxygen-vector) in the fermentation medium of A. terreus can significantly improve the bioprocess performance and enhance α-amylase production. Using 5% n-dodecane at 35 °C, an increase of 1.8–2 times in the enzymatic activity was recorded. In the oxygen-vector’s absence, the highest amount of biomass was obtained at 35 °C, while in the presence of 5% vol. n-dodecane, the amount of fungal biomass increased by approximately 70%, with a shift in optimum temperature to 40 °C, generating also an enzymatic activity increase of 2.30 times. Moreover, the oxygen-vector’s addition in the fermentation broth influenced the fungal morphological development in the form of larger pellets with a more compact structure compared to the system without n-dodecane, with a positive effect on the fermentation performance (higher α-amylase activity production).

Optimization of Alpha-Amylase Production by a Local Bacillus paramycoides Isolate and Immobilization on Chitosan-Loaded Barium Ferrite Nanoparticles

We set out to isolate alpha-amylase producers from soil samples, optimize the production, and immobilize the enzyme on chitosan-loaded barium ferrite nanoparticles (CLBFNPs). Alpha-amylase producers were isolated on starch agar plates and confirmed by dinitrosalicylic acid assay. The potent isolate was identified by phenotypic methods, 16S-rRNA sequencing, and phylogenetic mapping. Sequential optimization of α-amylase production involved the use of Plackett–Burman (P–BD) and central composite designs (CCD), in addition to exposing the culture to different doses of gamma irradiation. Alpha-amylase was immobilized on CLBFNPs, and the nanocomposite was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy, with energy-dispersive analysis of X-ray analysis. Forty-five α-amylase producers were isolated from 100 soil samples. The highest activity (177.12 ± 6.12 U/mg) was detected in the MS009 isolate, which was identified as Bacillus paramycoides. The activity increased to 222.3 ± 5.07 U/mg when using the optimal culture conditions identified by P–BD and CCD, and to 319.45 ± 4.91 U/mg after exposing the culture to 6 kGy. Immobilization of α-amylase on CLBFNPs resulted in higher activity (246.85 ± 6.76 U/mg) compared to free α-amylase (222.254 ± 4.89 U/mg), in addition to retaining activity for up to five cycles of usage. Gamma irradiation improved α-amylase production, while immobilization on CLBFNPs enhanced activity, facilitated enzyme recovery, and enabled its repetitive use.

Fungal biorefinery for sustainable resource recovery from waste

Depletion of natural resources and negative impact of fossil fuels on environment are becoming a global concern. The concept of biorefinery is one of the alternative platforms for the production of biofuels and chemicals. Valorisation of biological resources through complete utilization of waste, reusing secondary products and generating energy to power the process are the key principles of biorefinery. Agricultural residues and biogenic municipal solid wastes are getting importance as a potential feedstock for the generation of bioproducts. This communication reviews and highlights the scope of yeast and fungi as a potent candidate for the synthesis of gamut of bioproducts in an integrated approach addressing sustainability and circular bioeconomy. It also provides a close view on importance of microbes in biorefinery, feedstock pretreatment strategies for renewable sugar production, cultivation systems and yeast and fungi based products. Integrated closed loop approach towards multiple product generation with zero waste discharge is also discussed.

Hydrolytic enzyme production from açai palm (Euterpe precatoria) endophytic fungi and characterization of the amylolytic and cellulolytic extracts

Enzymes are biocatalysts that are widely used in different industries and generate billions of dollars annually. With the advancement of biotechnology, new enzymatic sources are being evaluated, especially microbial ones, in order to find efficient producers. Endophytic fungi are promising sources of biomolecules; however, Amazonian species are still poorly studied as to their enzymatic production potential. In this sense, the production of hydrolases (amylases, lipases, cellulases and pectinases) was evaluated in endophytic fungi isolated from the leaves, roots and stems of açai palms (Euterpe precatoria). A qualitative test was carried out to detect the enzymatic synthesis in each isolate, and the most promising ones were cultivated using submerged fermentation. The enzyme extracts were quantified to determine those with the greatest activity. Cellulolytic and amylolytic extracts showed the highest enzymatic activities and were partially characterized. Among 50 isolates, 82.9% produced pectinase, 58.5% produced cellulase, 31.7% produced amylase, and 12.2% produced lipase. Penicillium sp. L3 was the best producer of amylase and Colletotrichum sp. S1 was the best producer of cellulase in liquid medium cultivation. The amylolytic extract showed the highest enzymatic activity at pH 8.0 and 45 °C, and the cellulolytic extract at pH 5.0 and 35 °C. The cellulase and amylase produced by the endophytes had their molecular masses estimated between 38 and 76 kDa. These results indicate that endophytic fungi from the açai palm can be used as a new source of hydrolytic enzymes, which can be applied in numerous biotechnological processes.

Production and Partial Characterization of α-Amylase Enzyme from Marine Actinomycetes

Amylase producing actinobacteria were isolated and characterized from terrestrial environment. There are a limited number of reports investigating the marine environment; hence, in the present study, four marine enzymes were tested for their amylase production ability. On starch agar plates, the Streptomyces rochei strain showed a higher hydrolytic zone (24 mm) than the other isolates. Growth under optimized culture conditions using Plackett-Burman's experimental design led to a 1.7, 9.8, 7.7, and 3.12-fold increase for the isolates S. griseorubens, S. rochei, S. parvus, and Streptomyces sp., respectively, in the specific activity measurement. When applying the Box-Behnken design on S. rochei using the most significant parameters (starch, K₂HPO₄, pH, and temperature), there was a 12.22-fold increase in the specific activity measurement 7.37 U/mg. The α-amylase was partially purified, and its molecular weight was determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. α-Amylase was particularly active at pH 6 and 65°C. The purified enzyme was most active at 65°C and pH 6, thermal stability of 70°C for 40 min, and salt concentration of 1 M with Km and Vmax of 6.58 mg/ml and 21.93 μmol/ml/min, respectively. The α-amylase was improved by adding Cu⁺², Zn⁺², and Fe⁺² (152.21%, 207.24%, and 111.89%). Increased production of α-amylase enzyme by S. rochei KR108310 leads to production of significant industrial products.

Genomic Analysis of the 1-Aminocyclopropane-1-Carboxylate Deaminase-Producing Pseudomonas thivervalensis SC5 Reveals Its Multifaceted Roles in Soil and in Beneficial Interactions With Plants

Beneficial 1-aminocyclopropane-1-carboxylate (ACC) deaminase-producing bacteria promote plant growth and stress resistance, constituting a sustainable alternative to the excessive use of chemicals in agriculture. In this work, the increased plant growth promotion activity of the ACC deaminase-producing Pseudomonas thivervalensis SC5, its ability to limit the growth of phytopathogens, and the genomics behind these important properties are described in detail. P. thivervalensis SC5 displayed several active plant growth promotion traits and significantly increased cucumber plant growth and resistance against salt stress (100mmol/L NaCl) under greenhouse conditions. Strain SC5 also limited the in vitro growth of the pathogens Botrytis cinerea and Pseudomonas syringae DC3000 indicating active biological control activities. Comprehensive analysis revealed that P. thivervalensis SC5 genome is rich in genetic elements involved in nutrient acquisition (N, P, S, and Fe); osmotic stress tolerance (e.g., glycine-betaine, trehalose, and ectoine biosynthesis); motility, chemotaxis and attachment to plant tissues; root exudate metabolism including the modulation of plant phenolics (e.g., hydroxycinnamic acids), lignin, and flavonoids (e.g., quercetin); resistance against plant defenses (e.g., reactive oxygens species-ROS); plant hormone modulation (e.g., ethylene, auxins, cytokinins, and salicylic acid), and bacterial and fungal phytopathogen antagonistic traits (e.g., 2,4-diacetylphloroglucinol, HCN, a fragin-like non ribosomal peptide, bacteriocins, a lantipeptide, and quorum-quenching activities), bringing detailed insights into the action of this versatile plant-growth-promoting bacterium. Ultimately, the combination of both increased plant growth promotion/protection and biological control abilities makes P. thivervalensis SC5 a prime candidate for its development as a biofertilizer/biostimulant/biocontrol product. The genomic analysis of this bacterium brings new insights into the functioning of Pseudomonas and their role in beneficial plant-microbe interactions.

Utilization of starch effluent from a textile industry as a fungal growth supplement for enhanced α-amylase production for industrial application

Desizing process in textile industry produces large volume of starch effluent. This carbon-rich waste can be used for resource recovery, such as the production of industrially useful enzymes. The present work assesses the usability of starch effluent from textile industry as an additional carbon source for enhanced production of α-amylase during solid-state fermentation (SSF) of agro-wastes by Trichoderma reesei. A significant increase (p ≤ 0.05) in α-amylase activity (25.48 ± 1.12 U mL^-1) was observed with supplementation of starch effluent in SSF. Partial purification of α-amylase by 80% ammonium sulphate precipitation produced a yield of 58.39% enzyme with purification fold of 1.89. The enzyme was thermally stable at 40 °C with 90% residual activity after 5 h and 70% residual activity at 50 °C after 3 h. Using Michaelis-Menten kinetics analysis, the estimated K_m and V_max values for the partially purified α-amylase were found to be 2.55 mg mL^-1 and 53.47 U mg^-1, respectively. For the rapid assessment of the industrial application, desizing of the fabric was attempted. The cotton fabric was efficiently desized using α-amylase (at a concentration of 1% on the weight of fabric basis) at 80 °C. The present work demonstrates starch effluent from desizing process as a resource for the production of amylase. The amylase can further be used in the desizing process. With in-depth research, the work may lead to the development of a closed-loop, waste-recycling process for the textile industry.

Regulation of β-amylase synthesis: a brief overview

BACKGROUND

The major activity of β-amylase (BMY) is the production of maltose by the hydrolytic degradation of starch. BMY is found to be produced by some plants and few microorganisms only. The industrial importance of the enzyme warrants its application in a larger scale with the help of genetic engineering, for which the regulatory mechanism is to be clearly understood.

RESULTS AND CONCLUSION

In plants, the activities of BMY are regulated by various environmental stimuli including stress of drought, cold and heat. In vascular plant, Arabidopsis sp. the enzyme is coded by nine BAM genes, whereas in most bacteria, BMY enzymes are coded by the spoII gene family. The activities of these genes are in turn controlled by various compounds. Production and inhibition of the microbial BMY is regulated by the activation and inactivation of various BAM genes. Various types of transcriptional regulators associated with the plant- BMYs regulate the production of BMY enzyme. The enhancement in the expression of such genes reflects evolutionary significance. Bacterial genes, on the other hand, as exemplified by Bacillus sp and Clostridium sp, clearly depict the importance of a single regulatory gene, the absence or mutation of which totally abolishes the BMY activity.

Thalassobacillus, a genus of extreme to moderate environmental halophiles with biotechnological potential

Thalassobacillus is a moderately halophilic genus that has been isolated from several sites worldwide, such as hypersaline lakes, saline soils, salt flats, and volcanic mud. Halophilic bacteria have provided functional stable biomolecules in harsh conditions for industrial purposes. Despite its potential biotechnological applications, Thalassobacillus has not been fully characterized yet. This review describes the Thalassobacillus genus, with the few species reported, pointing out its possible applications in enzymes (amylases, cellulases, xylanases, and others), biosurfactants, bioactive compounds, biofuels production, bioremediation, and plant growth promotion. The Thalassobacillus genus represents a little-explored biological resource but with a high potential.

Isolation and enzyme bioprospection of bacteria associated to Bruguiera cylindrica, a mangrove plant of North Sumatra, Indonesia

Mangrove-associated bacteria are of industrial interest due to their diverse and versatile enzyme properties. This study investigates the culturable bacteria from a wide range of habitat in a Bruguiera cylindrica mangrove ecosystem in North Sumatra. Screening of extracellular hydrolytic enzymes showed multiple potential traits in amylase, cellulase, chitinase, phosphatase, protease, and urease production by bacterial isolates. Molecular identification based on 16S rDNA region of a potential strain, Vibrio alginolyticus Jme3-20 is then reported as a newly proteolytic agent. The strain also showed a stable growth under salinity (NaCl) stress with considerable phosphate solubilization activities. Protease activity was enhanced by optimizing the 0.5 % (w/v) sucrose and soy peptone in the fermentation medium. SDS-PAGE and zymogram analysis showed the presence of a 35-kDa MW protease. Hence, our study revealed important insights into the bacterial diversity and activity in mangrove ecosystems, evidencing the importance of microbial exploration in this ecosystem.

Physiological Characteristics and Comparative Secretome Analysis of Morchella importuna Grown on Glucose, Rice Straw, Sawdust, Wheat Grain, and MIX Substrates

Morels (Morchella sp.) are economically important edible macro-fungi, which can grow on various synthetic or semi-synthetic media. However, the complex nutritional metabolism and requirements of these fungi remain ill-defined. This study, based on the plant biomass commonly used in the artificial cultivation of morels, assessed and compared the growth characteristics and extracellular enzymes of Morchella importuna cultivated on glucose, rice straw, sawdust, wheat grain, and a mixture of equal proportions of the three latter plant substrates (MIX). M. importuna could grow on all five tested media but displayed significant variations in mycelial growth rate, biomass, and sclerotium yield on the different media. The most suitable medium for M. importuna was wheat and wheat-containing medium, followed by glucose, while rice straw and sawdust were the least suitable. A total of 268 secretory proteins were identified by liquid chromatography coupled with tandem mass spectrometry detection. Functional classification and label-free comparative analysis of these proteins revealed that carbohydrate-active enzyme (CAZYme) proteins were the predominant component of the secretome of M. importuna, followed by protease, peptidase, and other proteins. The abundances of CAZYme proteins differed among the tested media, ranging from 64% on glucose to 88% on rice straw. The CAZYme classes of glycoside hydrolases and carbohydrate-binding module were enriched in the five secretomes. Furthermore, the enzyme activities of CMCase, lignase, amylase, xylase, pNPCase, and pNPGase were detected during the continuous culture of M. importuna in MIX medium, and the relative expression of the corresponding genes were detected by quantitative real-time PCR. The combined data of growth potential, secretome, extracellular enzyme activity, and gene expression on different substrates inferred that M. importuna was weak in lignocellulose degradation but a good starch decomposer. Specifically, in terms of the degradation of cellulose, the ability to degrade cellulose into oligosaccharides was weaker compared with further degradation into monosaccharides, and this might be the speed-limiting step of cellulose utilization in M. importuna. In addition, M. importuna had a strong ability to decompose various hemicellulose glycosidic bonds, especially α- and β-galactosidase. Only a very few lignin-degradation-related proteins were detected, and these were in low abundance, consistent with the presence of weak lignin degradation ability. Furthermore, the presence of lipase and chitinase implied that M. importuna was capable of decomposition of its own mycelia in vitro. The study provides key data that facilitates a further understanding of the complex nutritional metabolism of M. importuna.

Bacterial α-diglucoside metabolism: perspectives and potential for biotechnology and biomedicine

In a competitive microbial environment, nutrient acquisition is a major contributor to the survival of any individual bacterial species, and the ability to access uncommon energy sources can provide a fitness advantage. One set of soluble carbohydrates that have attracted increased attention for use in biotechnology and biomedicine is the α-diglucosides. Maltose is the most well-studied member of this class; however, the remaining four less common α-diglucosides (trehalose, kojibiose, nigerose, and isomaltose) are increasingly used in processed food and fermented beverages. The consumption of trehalose has recently been shown to be a contributing factor in gut microbiome disease as certain pathogens are using α-diglucosides to outcompete native gut flora. Kojibiose and nigerose have also been examined as potential prebiotics and alternative sweeteners for a variety of foods. Compared to the study of maltose metabolism, our understanding of the synthesis and degradation of uncommon α-diglucosides is lacking, and several fundamental questions remain unanswered, particularly with regard to the regulation of bacterial metabolism for α-diglucosides. Therefore, this minireview attempts to provide a focused analysis of uncommon α-diglucoside metabolism in bacteria and suggests some future directions for this research area that could potentially accelerate biotechnology and biomedicine developments. KEY POINTS: • α-diglucosides are increasingly important but understudied bacterial metabolites. • Kinetically superior α-diglucoside enzymes require few amino acid substitutions. • In vivo studies are required to realize the biotechnology potential of α-diglucosides.

Biochemical Characterization of the Amylase Activity from the New Haloarchaeal Strain Haloarcula sp. HS Isolated in the Odiel Marshlands

Alpha-amylases are a large family of α,1-4-endo-glycosyl hydrolases distributed in all kingdoms of life. The need for poly-extremotolerant amylases encouraged their search in extreme environments, where archaea become ideal candidates to provide new enzymes that are able to work in the harsh conditions demanded in many industrial applications. In this study, a collection of haloarchaea isolated from Odiel saltern ponds in the southwest of Spain was screened for their amylase activity. The strain that exhibited the highest activity was selected and identified as Haloarcula sp. HS. We demonstrated the existence in both, cellular and extracellular extracts of the new strain, of functional α-amylase activities, which showed to be moderately thermotolerant (optimum around 60 °C), extremely halotolerant (optimum over 25% NaCl), and calcium-dependent. The tryptic digestion followed by HPLC-MS/MS analysis of the partially purified cellular and extracellular extracts allowed to identify the sequence of three alpha-amylases, which despite sharing a low sequence identity, exhibited high three-dimensional structure homology, conserving the typical domains and most of the key consensus residues of α-amylases. Moreover, we proved the potential of the extracellular α-amylase from Haloarcula sp. HS to treat bakery wastes under high salinity conditions.

Volatile Organic Compound-Mediated Antifungal Activity of Pichia spp. and Its Effect on the Metabolic Profiles of Fermentation Communities

Volatile organic compounds (VOCs) are chemicals responsible for antagonistic activity between microorganisms. The impact of VOCs on microbial community succession of fermentation is not well understood. In this study, Pichia spp. were evaluated for VOC production as a part of antifungal activity during baijiu fermentation. The results showed that the abundance of Pichia in the defect group (agglomerated fermented grains) was lower than that in control group, and a negative interaction between Pichia and Monascus was determined (P < 0.05). In addition, the disruption of fungi was significantly related to the differences of metabolic profiles in fermented grains. To determine production of VOCs from Pichia and its effect on Monascus purpureus, a double-dish system was assessed, and the incidence of M. purpureus reduction was 39.22% after 7 days. As to antifungal volatile compounds, 2-phenylethanol was identified to have an antifungal effect on M. purpureus through contact and noncontact. To further confirm the antifungal activity of 2-phenylethanol, scanning electron microscopy showed that 2-phenylethanol widely and significantly inhibited conidium germination and mycelial growth of filamentous fungi. Metatranscriptomic analysis revealed that the Ehrlich pathway is the metabolic path of 2-phenylethanol in Pichia and identified potential antifungal mechanisms, including protein synthesis and DNA damage. This study demonstrated the role of volatile compound-mediated microbial interaction in microbiome assembly and discovered a plausible scenario in which Pichia antagonized fungal blooms. The results may improve the niche establishment and growth of the functional yeast that enhances the flavor of baijiu.IMPORTANCE Fermentation of food occurs within communities of interacting species. The importance of microbial interactions in shaping microbial structure and metabolic performance to optimize the traditional fermentation process has long been emphasized, but the interaction mechanisms remain unclear. This study applied metabolome analysis and amplicon sequencing along with metatranscriptomic analysis to examine the volatile organic compound-mediated antifungal activity of Pichia and its effect on the metabolism of ethanol during baijiu fermentation, potentially enhancing the establishment of the fermentation niche and improving ethanol metabolism.

Acid stable α-amylase from Pseudomonas balearica VITPS19-Production, purification and characterization

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α – Amylase was produced from a rhizobacteria Pseudomonas balearica VITPS19.

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One factor at a time method (OFAT) was employed to optimize the α –amylase production.

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Three step purification of α – amylase from the fermentation broth.

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Determining the optimal conditions for enzyme activity.

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Estimation of the enzymatic kinetic parameters of the α-amylase.

In the present study, α-amylase from Pseudomonas balearica VITPS19 isolated from Kolathur, Tamil Nadu, India was studied. Initially, one factor at a time (OFAT) approach was used to optimize the medium parameters like pH, temperature, carbon and nitrogen sources and the presence of metal ions to enhance the amylase activity. After the optimization, 6.5-fold increase in the enzyme production was observed. Enzyme purification was carried out in three stages. The molecular weight of purified α-amylase was estimated to be 47 kDa.The optimum activity for the purified enzyme was observed at pH 6 in 0.1 M phosphate buffer at 25 ± 2 °C and the activity is enhanced in the presence of ions like Mn²⁺, Mo⁶⁺, Na⁺, Mg²⁺and Zn²⁺ and was inhibited in the presence of Hg²⁺ ions. Compounds such as Sodium dodecyl sulfate (SDS), Ethylenediaminetetraacetic acid (EDTA), urea and β- mercaptoethanol reduced the amylase activity. The K_m and V_max of the α-amylase was estimated to be 45.23 mM and 20.83 U/mL, respectively.

Diverse activities and biochemical properties of amylase and proteases from six freshwater fish species

This study investigated the biochemical properties, enzyme activities, isoenzyme pattern, and molecular weight of three types of digestive enzyme from six freshwater fish species: Puntius gonionotus (common silver barb), Puntioplites proctozysron (Smith’s barb), Oreochromis niloticus (Nile tilapia), Hemibagrus spilopterus (yellow mystus), Ompok bimaculatus (butter catfish), and Kryptopterus geminus (sheatfish). The optimum pHs for amylase and alkaline protease activities were 7.0–8.0 and 8.0–10.0, and the optimum temperatures were 45–60 °C and 50–55 °C, respectively. A pepsin-like enzyme was detected in all three carnivorous fishes (Ompok bimaculatus, Kryptopterus geminus, and Hemibagrus spilopterus) with optimum reaction pH of 2.0 for each and optimum reaction temperatures 50–55 °C. In optimum reaction conditions, the amylase and alkaline protease from Puntioplites proctozyron showed the highest activities. Lower activities of all enzymes were observed at temperature (29 °C) of Lam Nam Choen swamp than at the optimum reaction temperatures. The fish species contained one to three and five to eight isoforms of amylase and alkaline protease, respectively, with molecular weights from 19.5 to 175 kDa. Both the alkaline proteases and amylases were stable in wide pH and temperature ranges.

Biosynthesis and industrial applications of α-amylase: a review

Amylase is amongst the most indispensable enzymes that have a large number of applications in laboratories and industries. Mostly, α-amylase is synthesized from microbes such as bacteria, fungi and yeast. Due to the high demand for α-amylase, its synthesis can be enhanced using recombinant DNA technology, different fermentation methods, less expensive and good carbon and nitrogen sources, and optimizing the various parameters during fermentation, e.g., temperature, pH and fermentation duration. Various methods are used to measure the production and activity of synthesized α-amylase like iodine, DNS, NS and dextrinizing methods. The activity of crude α-amylase can be elevated to the maximum level by optimizing the temperature and pH. Some metals also interact with α-amylase and increase its activity like K⁺, Na⁺, Mg²⁺ and Ca²⁺. Some industries such as starch conversion, food, detergent, paper, textile industries and fuel alcohol production extensively utilize α-amylase for their various purposes.

Recombinant expression, purification, and characterization of an α-amylase from Massilia timonae

This work reports the amy1 gene cloning from Massilia timonae CTI-57, and its successful expression in Escherichia coli Rosetta™ (DE3) from the pTRCHis2B plasmid. The recombinant AMY1 protein had 47 kDa, and its modeled structure showed a monomer composed of three domains. An N-terminal domain with the characteristic (β/α)₈-barrel structure of α-amylases, which contained the catalytic amino acid residues. The second domain was small, and the C-terminal domain was similar to those found in the barley α-amylase. A phylogenetic analysis demonstrated a high sequence identity of the studied protein with bacterial and plant α-amylases from the GH13_6 subfamily. This is the first characterized bacterial α-amylase from this glucoside hydrolase subfamily. Besides starch, the enzyme was also active against maltodextrin, amylopectin, and blocked p-nitrophenyl α-d-maltoheptaoside, but could not use β-cyclodextrin or 4-nitrophenyl α-d-glucopyranoside. The K _M for highly pure grade soluble starch from potato and V _max values were 0.79 mg/mL and 0.04 mg/min, respectively. The calcium ion showed to be essential for the purified enzyme's activity, while EDTA, molybdenum, cobalt, and mercury were strong inhibitors. The enzyme was almost fully active in SDS presence. The enzyme's optimal pH and temperature were 6.0 and 60 °C, respectively, and its denaturation T _m was 79 °C. A TLC analysis revealed that glucose and maltose are products of the enzyme's action on starch. In conclusion, this work described the M. timonae GH13_6 subfamily α-amylase, which showed to be thermostable and anionic detergent-resistant.

Resistant starch, microbiome, and precision modulation

Resistant starch, microbiome, and precision modulation. Mounting evidence has positioned the gut microbiome as a nexus of health. Modulating its phylogenetic composition and function has become an attractive therapeutic prospect. Resistant starches (granular amylase-resistant α-glycans) are available as physicochemically and morphologically distinguishable products. Attempts to leverage resistant starch as microbiome-modifying interventions in clinical studies have yielded remarkable inter-individual variation. Consequently, their utility as a potential therapy likely depends predominantly on the selected resistant starch and the subject's baseline microbiome. The purpose of this review is to detail i) the heterogeneity of resistant starches, ii) how resistant starch is sequentially degraded and fermented by specialized gut microbes, and iii) how resistant starch interventions yield variable effects on the gut microbiome.