A novel bacterial type II l -asparaginase and evaluation of its enzymatic acrylamide reduction in French fries

Identification of a thermostable L-asparaginase from Pyrococcus yayanosii CH1 and its application in the reduction of acrylamide

L-asparaginase (ASNase, E.C. 3.5.1.1) catalyzes the deamination of L-asparagine to L-aspartic acid and ammonia and is widely used in medicine to treat acute lymphocytic leukemia. It also has significant applications in the food industry by inhibiting acrylamide formation. In this study, we characterized a thermostable ASNase from the hyper thermophilic strain, Pyrococcus yayanosii CH1. The recombinant enzyme (PyASNase) exhibited maximal activity at pH 8.0 and 85 °C. Moreover, PyASNase demonstrated promising thermostability across temperatures ranging from 70 to 95 °C. The kinetic parameters of PyASNase for L-asparagine were a Km of 6.3 mM, a kcat of 1989s-1, and a kcat/Km of 315.7 mM-1 s-1. Treating potato samples with 10 U/mL of PyASNase at 85 °C for merely 10 min reduced the acrylamide content in the final product by 82.5%, demonstrating a high efficiency and significant advantage of PyASNase in acrylamide inhibition.

Mitigation of acrylamide in fried food systems using a combination of zein-pectin hydrocolloid complex and a food-grade l-asparaginase

Acrylamide, a Maillard reaction product, formed in fried food poses a serious concern to food safety due to its neurotoxic and carcinogenic nature. A "Green Approach" using L-Asparaginase enzyme from GRAS-status bacteria synergized with hydrocolloid protective coating could be effective in inhibiting acrylamide formation. To fill this void, the present study reports a new variant of type-II L-asparaginase (AsnLb) from Levilactobacillus brevis NKN55, a food-grade bacterium isolated using a unique metabolite profiling approach. The recombinant AsnLb enzyme was characterized to study acrylamide inhibition ability and showed excellent specificity towards L-asparagine (157.2 U/mg) with Km, Vmax of 0.833 mM, 4.12 mM/min respectively. Pretreatment of potato slices with AsnLb (60 IU/mL) followed by zein-pectin nanocomplex led to >70% reduction of acrylamide formation suggesting synergistic effect of this dual component system. The developed strategy can be employed as a sustainable treatment method by food industries for alleviating acrylamide formation and associated health hazard in fried foods.

Identification and Thermostability Modification of the Mesophilic L-asparaginase from Limosilactobacillus secaliphilus

L-asparaginase (L-ASNase, E.C.3.5.1.1) could effectively inhibit the formation of acrylamide (AA) by hydrolyzing the AA precursor L-asparagine. However, most of the L-ASNases showed a relatively weak thermostability, posing a big threat on the application of enzyme at high processing temperatures. Here, the recombinant L-ASNase from mesophilic bacteria Limosilactobacillus secaliphilus was identified for the first time. The recombinant enzyme exhibited its optimal activity at pH 8.0 and 60 ℃. Additionally, the thermostability of L. secaliphilus L-ASNase was enhanced by site-directed mutagenesis after multiple sequence alignment. Ten mutants were reasonably constructed, among which the single-point mutants L24Y, S55T, and V155S showed more than 1 ℃ elevated Tm value compared to the wild-type enzyme. In addition, the half-life of mutant at 40, 50, and 55 ℃ was 376.7 min, 62.1 min, and 18.7 min, much higher than that of wild-type enzyme. The molecular dynamic simulation showed that compared to the wild-type enzyme, the structural stability of V155S was greatly strengthened due to the lower RMSF and RMSD value as well as a decreased total energy compared to that of the wild-type enzyme. The results were positive and provided some useful information for the thermostability modification of L-ASNase.

A novel type IIb L-asparaginase from Latilactobacillus sakei LK-145: characterization and application

We succeeded in homogeneously expressing and purifying L-asparaginase from Latilactobacillus sakei LK-145 (Ls-Asn1) and its mutated enzymes C196S, C264S, C290S, C196S/C264S, C196S/C290S, C264S/C290S, and C196S/C264S/C290S-Ls-Asn1. Enzymological studies using purified enzymes revealed that all cysteine residues of Ls-Asn1 were found to affect the catalytic activity of Ls-Asn1 to varying degrees. The mutation of Cys196 did not affect the specific activity, but the mutation of Cys264, even a single mutation, significantly decreased the specific activity. Furthermore, C264S/C290S- and C196S/C264S/C290S-Ls-Asn1 almost completely lost their activity, suggesting that C290 cooperates with C264 to influence the catalytic activity of Ls-Asn1. The detailed enzymatic properties of three single-mutated enzymes (C196S, C264S, and C290S-Ls-Asn1) were investigated for comparison with Ls-Asn1. We found that only C196S-Ls-Asn1 has almost the same enzymatic properties as that of Ls-Asn1 except for its increased stability for thermal, pH, and the metals NaCl, KCl, CaCl2, and FeCl2. We measured the growth inhibitory effect of Ls-Asn1 and C196S-Ls-Asn1 on Jurkat cells, a human T-cell acute lymphoblastic leukemia cell line, using L-asparaginase from Escherichia coli K-12 as a reference. Only C196S-Ls-Asn1 effectively and selectively inhibited the growth of Jurkat T-cell leukemia, which suggested that it exhibited antileukemic activity. Furthermore, based on alignment, phylogenetic tree analysis, and structural modeling, we also proposed that Ls-Asn1 is a so-called "Type IIb" novel type of asparaginase that is distinct from previously reported type I or type II asparaginases. Based on the above results, Ls-Asn1 is expected to be useful as a new leukemia therapeutic agent.

In vitro and in silico analysis unravelled clinically desirable attributes of Bacillus altitudinis L-asparaginase

AIMS

To identify a marine L-asparaginase with clinically desirable attributes and characterize the shortlisted candidate through in silico tools.

METHODS AND RESULTS

Marine bacterial strains (number = 105) isolated from marine crabs were evaluated through a stepwise strategy incorporating the crucial attributes for therapeutic safety. The results demonstrated the potential of eight bacterial species for extracellular L-asparaginase production. However, only one isolate (Bacillus altitudinis CMFRI/Bal-2) showed clinically desirable attributes, viz. extracellular production, type-II nature, lack of concurrent L-glutaminase and urease activities, and presence of ansZ (functional gene for clinical type). The enzyme production was 22.55 ± 0.5 µM/mg protein/min within 24 h without optimization. The enzyme also showed good activity and stability in pH 7-8 and temperature 37°C, predicting the functioning inside the human body. The Michealis-Menten constant (Km) was 14.75 µM. Detailed in silico analysis based on functional gene authenticating the results of in vitro characterization and predicted the nonallergenic characteristic of the candidate. Docking results proved the higher affinity of the shortlisted candidate to L-asparagine than L-glutamine and urea.

CONCLUSION

Comprehensively, the study highlighted B. altitudinis type II asparaginase as a competent candidate for further research on clinically safe asparaginases.

Evaluation of the efficiency of thermostable L-asparaginase from B. licheniformis UDS-5 for acrylamide mitigation during preparation of French fries

A thermostable L-asparaginase was produced from Bacillus licheniformis UDS-5 (GenBank accession number, OP117154). The production conditions were optimized by the Plackett Burman method, followed by the Box Behnken method, where the enzyme production was enhanced up to fourfold. It secreted L-asparaginase optimally in the medium, pH 7, containing 0.5% (w/v) peptone, 1% (w/v) sodium chloride, 0.15% (w/v) beef extract, 0.15% (w/v) yeast extract, 3% (w/v) L-asparagine at 50 °C for 96 h. The enzyme, with a molecular weight of 85 kDa, was purified by ion exchange chromatography and size exclusion chromatography with better purification fold and percent yield. It displayed optimal catalysis at 70 °C in 20 mM Tris-Cl buffer, pH 8. The purified enzyme also exhibited significant salt tolerance too, making it a suitable candidate for the food application. The L-asparaginase was employed at different doses to evaluate its ability to mitigate acrylamide, while preparing French fries without any prior treatment. The salient attributes of B. licheniformis UDS-5 L-asparaginase, such as greater thermal stability, salt stability and acrylamide reduction in starchy foods, highlights its possible application in the food industry.

Biochemical characterization of glutaminase-free L-asparaginases from Himalayan Pseudomonas and Rahnella spp. for acrylamide mitigation

L-asparaginase having low glutaminase activity is important in clinical and food applications. Herein, glutaminase-free L-asparaginase (type I) coding genes from Pseudomonas sp. PCH182 (Ps-ASNase I) and Rahnella sp. PCH162 (Rs-ASNase I) was amplified using gene-specific primers, cloned into a pET-47b(+) vector, and plasmids were transformed into Escherichia coli (E. coli). Further, affinity chromatography purified recombinant proteins to homogeneity with monomer sizes of ~37.0 kDa. Purified Ps-ASNase I and Rs-ASNase I were active at wide pHs and temperatures with optimum activity at 50 °C (492 ± 5 U/mg) and 37 °C (308 ± 4 U/mg), respectively. Kinetic constant Km and Vmax for L-asparagine (Asn) were 2.7 ± 0.06 mM and 526.31 ± 4.0 U/mg for Ps-ASNase I, and 4.43 ± 1.06 mM and 434.78 ± 4.0 U/mg for Rs-ASNase I. Circular dichroism study revealed 29.3 % and 24.12 % α-helix structures in Ps-ASNase I and Rs-ASNase I, respectively. Upon their evaluation to mitigate acrylamide formation, 43 % and 34 % acrylamide (AA) reduction were achieved after pre-treatment of raw potato slices, consistent with 65 % and 59 % Asn reduction for Ps-ASNase I and Rs-ASNase I, respectively. Current findings suggested the potential of less explored intracellular L-asparaginase in AA mitigation for food safety.

Toxicity, metabolism, and mitigation strategies of acrylamide: a comprehensive review

Acrylamide, a food-borne chemical toxicant, has raised global concern in recent decades. It mainly originated from reducing sugar and free amino acid interactions in the carbohydrate-rich foodstuffs heated at high temperatures. Due to the neurotoxicity and carcinogenicity of AA, the mechanism of formation, toxic effects on health, and mitigation strategies, including conventional approaches and innovative technologies, have been of great interest since its discovery in food. Potato products (especially French fries and crisps), coffee, and cereals(bread and biscuit) are renowned contributors to AA's daily intake. The best preventive methods discussed in the literature include time/temperature optimization, blanching, enzymatic treatment, yeast treatment, additives, pulsed electric fields, ultrasound, vacuum roasting, air frying, and irradiation, exhibiting a high efficacy in AA elimination in food products.

Thermal Stability Enhancement of L-Asparaginase from Corynebacterium glutamicum Based on a Semi-Rational Design and Its Effect on Acrylamide Mitigation Capacity in Biscuits

Acrylamide is present in thermally processed foods, and it possesses toxic and carcinogenic properties. L-asparaginases could effectively regulate the formation of acrylamide at the source. However, current L-asparaginases have drawbacks such as poor thermal stability, low catalytic activity, and poor substrate specificity, thereby restricting their utility in the food industry. To address this issue, this study employed consensus design to predict the crucial residues influencing the thermal stability of Corynebacterium glutamicum L-asparaginase (CgASNase). Subsequently, a combination of site-point saturating mutation and combinatorial mutation techniques was applied to generate the double-mutant enzyme L42T/S213N. Remarkably, L42T/S213N displayed significantly enhanced thermal stability without a substantial impact on its enzymatic activity. Notably, its half-life at 40 °C reached an impressive 13.29 ± 0.91 min, surpassing that of CgASNase (3.24 ± 0.23 min). Moreover, the enhanced thermal stability of L42T/S213N can be attributed to an increased positive surface charge and a more symmetrical positive potential, as revealed by three-dimensional structural simulations and structure comparison analyses. To assess the impact of L42T/S213N on acrylamide removal in biscuits, the optimal treatment conditions for acrylamide removal were determined through a combination of one-way and orthogonal tests, with an enzyme dosage of 300 IU/kg flour, an enzyme reaction temperature of 40 °C, and an enzyme reaction time of 30 min. Under these conditions, compared to the control (464.74 ± 6.68 µg/kg), the acrylamide reduction in double-mutant-enzyme-treated biscuits was 85.31%, while the reduction in wild-type-treated biscuits was 68.78%. These results suggest that L42T/S213N is a promising candidate for industrial applications of L-asparaginase.

Effective mitigation in the amount of acrylamide through enzymatic approaches

Acrylamide (AA), as a food-borne toxicant, is created at some stages of thermal processing in the starchy food through Maillard reaction, fatty food via acrolein route, and proteinous food using free amino acids pathway. Maillard reaction obviously takes place in thermal-based products, being responsible for specific sensory attributes; AA formation, thereby, is unavoidable during the thermal processing. Additionally, AA can naturally occur in soil and water supply. In order to reduce the levels of acrylamide in cooked foods, mitigation techniques can be separated into three different types. Firstly, starting materials low in acrylamide precursors can be used to reduce the acrylamide in the final product. Secondly, process conditions may be modified in order to decrease the amount of acrylamide formation. Thirdly, post-process intervention could be used to reduce acrylamide. Conventional or emerging mitigation techniques might negatively influence the pleasant features of heated foods. The current study summarizes the effect of enzymatic reaction induced by asparaginase, glucose oxidase, acrylamidase, phytase, amylase, and protease to possibly inhibit AA formation or progressively hydrolyze formed AA. Not only enzyme-assisted AA reduction could dramatically maintain bio-active compounds, but also no damaging impact has been reported on the sensorial and rheological properties of the final heated products. The enzyme engineering can be applied to ameliorate enzyme functionality through altering the amino acid sequence like site-specific mutagenesis and directed evolution, chemical modifications by covalent conjugation of L-asparaginase onto soluble/insoluble biocompatible polymers and immobilization. Moreover, it would be possible to improve the enzyme's physical, chemical, and thermal stability, recyclability and prevent enzyme overuse by applying engineered ones. In spite of enzymes' cost-effective and eco-friendly, promoting their large-scale usages for AA reduction in food application and AA bioremediation in wastewater and soil resources.

Characterization of L-asparaginase from Streptomyces koyangensis SK4 with acrylamide-minimizing potential in potato chips

Microbial L-asparaginase is well known for its application in food industries to reduce acrylamide content in fried starchy food. L-asparaginase produced by Arctic actinomycetes Streptomyces koyangensis SK4 was purified and studied for biochemical characterization. The L-asparaginase was purified with a yield of 15.49% and final specific activity of 179.77 IU/mg of protein. The enzyme exhibited a molecular weight of 43 kDa. The optimum pH and temperature for maximum activity of the purified enzyme were 8.5 °C and 40 °C, respectively. The enzyme expressed maximum activity at an incubation period of 30 min and a substrate concentration of 0.06 M. The enzyme has a low Km value of 0.041 M and excellent substrate specificity toward L-asparagine. The enzyme activity was inhibited by metal ions Ba2+ and Hg2+, while Mn2+ and Mg2+ enhanced the activity. The study evaluated the acrylamide reduction potential of L-asparaginase from Streptomyces koyangensis SK4 in potato chips. The blanching plus L-asparaginase treatment of potato slices resulted in a 50% reduction in acrylamide content. The study illustrated an effective acrylamide reduction strategy in potato chips using L-asparaginase from a psychrophilic actinomycete. Besides the acrylamide reduction potential, L-asparaginase from Streptomyces koyangensis SK4 also did not exhibit any glutaminase or urease activity which is an outstanding feature of L-asparaginase to be used as a chemotherapeutic agent.

Molecular Characterization of a Stable and Robust L-Asparaginase from Pseudomonas sp. PCH199: Evaluation of Cytotoxicity and Acrylamide Mitigation Potential

L-asparaginase is an important industrial enzyme widely used to treat acute lymphoblastic leukemia (ALL) and to reduce acrylamide formation in food products. In the current study, a stable and robust L-asparaginase from Pseudomonas sp. PCH199, with a high affinity for L-asparagine, was cloned and expressed in Escherichia coli BL21(DE3). Recombinant L-asparaginase (Pg-ASNase II) was purified with a monomer size of 37.0 kDa and a native size of 148.0 kDa. During characterization, Pg-ASNase II exhibited 75.8 ± 3.84 U/mg specific activities in 50.0 mM Tris-HCl buffer (pH 8.5) at 50 °C. However, it retained 80 and 70% enzyme activity at 37 °C and 50 °C after 60 min, respectively. The half-life and kd values were 625.15 min and 1.10 × 10−3 min−1 at 37 °C. The kinetic constant Km, Vmax, kcat, and kcat/Km values were 0.57 mM, 71.42 U/mg, 43.34 s−1, and 77.90 ± 9.81 s−1 mM−1 for L-asparagine, respectively. In addition, the enzyme has shown stability in the presence of most metal ions and protein-modifying agents. Pg-ASNase II was cytotoxic towards the MCF-7 cell line (breast cancer) with an estimated IC50 value of 0.169 U/mL in 24 h. Further, Pg-ASNase II treatment led to a 70% acrylamide reduction in baked foods. These findings suggest the potential of Pg-ASNase II in therapeutics and the food industry.

Thermostability Improvement of L-Asparaginase from Acinetobacter soli via Consensus-Designed Cysteine Residue Substitution

To extend the application range of L-asparaginase in food pre-processing, the thermostability improvement of the enzyme is essential. Herein, two non-conserved cysteine residues with easily oxidized free sulfhydryl groups, Cys8 and Cys283, of Acinetobacter soli L-asparaginase (AsA) were screened out via consensus design. After saturation mutagenesis and combinatorial mutation, the mutant C8Y/C283Q with highly improved thermostability was obtained with a half-life of 361.6 min at 40 °C, an over 34-fold increase compared with that of the wild-type. Its melting temperature (T_m) value reaches 62.3 °C, which is 7.1 °C higher than that of the wild-type. Molecular dynamics simulation and structure analysis revealed the formation of new hydrogen bonds of Gln283 and the aromatic interaction of Tyr8 formed with adjacent residues, resulting in enhanced thermostability. The improvement in the thermostability of L-asparaginase could efficiently enhance its effect on acrylamide inhibition; the contents of acrylamide in potato chips were efficiently reduced by 86.50% after a mutant C8Y/C283Q treatment, which was significantly higher than the 59.05% reduction after the AsA wild-type treatment. In addition, the investigation of the mechanism behind the enhanced thermostability of AsA could further direct the modification of L-asparaginases for expanding their clinical and industrial applications.

Characterization of a novel and glutaminase-free type II L-asparaginase from Corynebacterium glutamicum and its acrylamide alleviation efficiency in potato chips

Type II L-asparaginase as a pivotal enzyme agent has been applied to treating for acute lymphoblastic leukemia (ALL) and efficient mitigation of acrylamide formed in fried and baked foods. However, low activity, narrow range of pH stability, as well as undesirable glutaminase activity hinder the applications of this enzyme. In our work, A novel type II L-asparaginase (CgASNase) from Corynebacterium glutamicum with molecular mass of about 35 kDa was chosen to express in E. coli. CgASNase shared only 27 % structural identity with the reported L-asparaginase from Helicobacter pylori. The purified CgASNase showed the highest specific activity of 1979.08 IU mg^-1 to L-asparagine, compared with reported type II ASNases in the literature. CgASNase displayed superior stability at a wide pH range from 5.0 to 11.0, and retained about 76 % of its activity at 30 °C for 30 min. The kinetic parameters K_m (Michaelis constant), k_cat (turnover number), and k_cat/K_m (catalytic efficiency) values of 4.66 mM, 79,697.40 min^-1, and 17,102.45 mM^-1 min^-1, respectively. More importantly, CgASNase exhibited strict substrate specificity towards L-asparagine, no detectable activity to l-glutamine. To explore its ability to catalyze L-asparagine, CgASNase was supplied in frying potato chips, which produced the fries with 84 % less acrylamide content compared with no supply. These findings suggest that CgASNase presents excellent properties for chemotherapy against diseases and great potential in the food processing industry.

A systematic review of recent trends in research on therapeutically significant L-asparaginase and acute lymphoblastic leukemia

L-asparaginases are mostly obtained from bacterial sources for their application in the therapy and food industry. Bacterial L-asparaginases are employed in the treatment of Acute Lymphoblastic Leukemia (ALL) and its subtypes, a type of blood and bone marrow cancer that results in the overproduction of immature blood cells. It also plays a role in the food industry in reducing the acrylamide formed during baking, roasting, and frying starchy foods. This importance of the enzyme makes it to be of constant interest to the researchers to isolate novel sources. Presently L-asparaginases from E. coli native and PEGylated form, Dickeya chrysanthemi (Erwinia chrysanthemi) are in the treatment regime. In therapy, the intrinsic glutaminase activity of the enzyme is a major drawback as the patients in treatment experience side effects like fever, skin rashes, anaphylaxis, pancreatitis, steatosis in the liver, and many complications. Its significance in the food industry in mitigating acrylamide is also a major reason. Acrylamide, a potent carcinogen was formed when treating starchy foods at higher temperatures. Acrylamide content in food was analyzed and pre-treatment was considered a valuable option. Immobilization of the enzyme is an advancing and promising technique in the effective delivery of the enzyme than in free form. The concept of machine learning by employing the Artificial Network and Genetic Algorithm has paved the way to optimize the production of L-asparaginase from its sources. Gene-editing tools are gaining momentum in the study of several diseases and this review focuses on the CRISPR-Cas9 gene-editing tool in ALL.

Cis-Element Engineering Promotes the Expression of Bacillus subtilis Type I L-Asparaginase and Its Application in Food

Type I L-asparaginase from Bacillus licheniformis Z-1 (BlAase) was efficiently produced and secreted in Bacillus subtilis RIK 1285, but its low yield made it unsuitable for industrial use. Thus, a combined method was used in this study to boost BlAase synthesis in B. subtilis. First, fifteen single strong promoters were chosen to replace the original promoter P43, with PyvyD achieving the greatest BlAase activity (436.28 U/mL). Second, dual-promoter systems were built using four promoters (PyvyD, P43, PaprE, and PspoVG) with relatively high BlAase expression levels to boost BlAase output, with the engine of promoter PaprE-PyvyD reaching 502.11 U/mL. The activity of BlAase was also increased (568.59 U/mL) by modifying key portions of the PaprE-PyvyD promoter. Third, when the ribosome binding site (RBS) sequence of promoter PyvyD was replaced, BlAase activity reached 790.1 U/mL, which was 2.27 times greater than the original promoter P43 strain. After 36 h of cultivation, the BlAase expression level in a 10 L fermenter reached 2163.09 U/mL, which was 6.2 times greater than the initial strain using promoter P43. Moreover, the application potential of BlAase on acrylamide migration in potato chips was evaluated. Results showed that 89.50% of acrylamide in fried potato chips could be removed when combined with blanching and BlAase treatment. These findings revealed that combining transcription and translation techniques are effective strategies to boost recombinant protein output, and BlAase can be a great candidate for controlling acrylamide in food processing.

Dual role of CsrA in regulating the hemolytic activity of Escherichia coli O157:H7

Post-transcriptional global carbon storage regulator A (CsrA) is a sequence-specific RNA-binding protein involved in the regulation of multiple bacterial processes. Hemolysin is an important virulence factor in the enterohemorrhagic Escherichia coli O157:H7 (EHEC). Here, we show that CsrA plays a dual role in the regulation of hemolysis in EHEC. CsrA significantly represses plasmid-borne enterohemolysin (EhxA)-mediated hemolysis and activates chromosome-borne hemolysin E (HlyE)-mediated hemolysis through different mechanisms. RNA structure prediction revealed a well-matched stem-loop structure with two potential CsrA binding sites located on the 5' untranslated region (UTR) of ehxB, which encodes a translocator required for EhxA secretion. CsrA inhibits EhxA secretion by directly binding to the RNA leader sequence of ehxB to repress its expression in two different ways: CsrA either binds to the Shine–Dalgarno sequence of ehxB to block ribosome access or to ehxB transcript to promote its mRNA decay. The predicted CsrA-binding site 1 of ehxB is essential for its regulation. There is a single potential CsrA-binding site at the 5'-end of the hlyE transcript, and its mutation completely abolishes CsrA-dependent activation. CsrA can also stabilize hlyE mRNA by directly binding to its 5' UTR. Overall, our results indicate that CsrA acts as a hemolysis modulator to regulate pathogenicity under certain conditions.

The Acrylamide Degradation by Probiotic Strain Lactobacillus acidophilus LA-5

Acrylamide is a harmful substance produced in thermal processed food; however, it can also be found in food with various additives. The aim of the study was to check whether the probiotic bacteria strain, Lactobacillus acidophilus LA-5 (LA5), can degrade acrylamide and hence reduce its concentration in foodstuff. Our results revealed that LA5 can degrade acrylamide and cause a decrease in its concentration, but only when other available carbon and nitrogen sources are lacking. In the presence of casein, lactose, milk fat or in whole cow’s milk, this ability disappeared. Acrylamide present in milk, however, modulated the bacteria metabolism by significantly enhancing lactic acid production by LA5 in milk (at conc. 100 µg/mL), while the production of acetic acid was rather reduced.

Characterization of a Novel L-Asparaginase from Mycobacterium gordonae with Acrylamide Mitigation Potential

L-asparaginase (E.C.3.5.1.1) is a well-known agent that prevents the formation of acrylamide both in the food industry and against childhood acute lymphoblastic leukemia in clinical settings. The disadvantages of L-asparaginase, which restrict its industrial application, include its narrow range of pH stability and low thermostability. In this study, a novel L-asparaginase from Mycobacterium gordonae (GmASNase) was cloned and expressed in Escherichia coli BL21 (DE3). GmASNase was found to be a tetramer with a monomeric size of 32 kDa, sharing only 32% structural identity with Helicobacter pylori L-asparaginases in the Protein Data Bank database. The purified GmASNase had the highest specific activity of 486.65 IU mg⁻¹ at pH 9.0 and 50 °C. In addition, GmASNase possessed superior properties in terms of stability at a wide pH range of 5.0–11.0 and activity at temperatures below 40 °C. Moreover, GmASNase displayed high substrate specificity towards L-asparagine with Km, kcat, and kcat/Km values of 6.025 mM, 11,864.71 min⁻¹ and 1969.25 mM⁻¹min⁻¹, respectively. To evaluate its ability to mitigate acrylamide, GmASNase was used to treat potato chips prior to frying, where the acrylamide content decreased by 65.09% compared with the untreated control. These results suggest that GmASNase is a potential candidate for applications in the food industry.

Microbial L-asparaginase for Application in Acrylamide Mitigation from Food: Current Research Status and Future Perspectives

L-asparaginase (E.C.3.5.1.1) hydrolyzes L-asparagine to L-aspartic acid and ammonia, which has been widely applied in the pharmaceutical and food industries. Microbes have advantages for L-asparaginase production, and there are several commercially available forms of L-asparaginase, all of which are derived from microbes. Generally, L-asparaginase has an optimum pH range of 5.0-9.0 and an optimum temperature of between 30 and 60 °C. However, the optimum temperature of L-asparaginase from hyperthermophilic archaea is considerable higher (between 85 and 100 °C). The native properties of the enzymes can be enhanced by using immobilization techniques. The stability and recyclability of immobilized enzymes makes them more suitable for food applications. This current work describes the classification, catalytic mechanism, production, purification, and immobilization of microbial L-asparaginase, focusing on its application as an effective reducer of acrylamide in fried potato products, bakery products, and coffee. This highlights the prospects of cost-effective L-asparaginase, thermostable L-asparaginase, and immobilized L-asparaginase as good candidates for food application in the future.

Microbial production, molecular modification, and practical application of l-Asparaginase: A review

L-Asparaginase (L-ASNase, EC 3.5.1.1), an antitumor drug for acute lymphoblastic leukemia (ALL) therapy, is widely used in the clinical field. Similarly, L-ASNase is also a powerful and significant biological tool in the food industry to inhibit acrylamide (AA) formation. This review comprehensively summarizes the latest achievements and improvements in the production, modification, and application of microbial L-ASNase. To date, the expression levels and optimization of expression hosts such as Escherichia coli, Bacillus subtilis, and Pichia pastoris, have made significant progress. In addition, examples of successful modification of L-ASNase such as decreasing glutaminase activity, increasing the in vivo stability, and enhancing thermostability have been presented. Impressively, the application of L-ASNase as a food addition aid, as well as its commercialization in the pharmaceutical field, and cutting-edge biosensor application developments have been summarized. The presented results and proposed ideas could be a good guide for other L-ASNase researchers in both scientific and practical fields.

Recent advances in biotechnology for marine enzymes and molecules

The marine environment is the most biologically and chemically diverse habitat on Earth, and provides numerous marine-derived products, including enzymes and molecules, for industrial and pharmaceutical applications. Marine biotechnology provides important biological resources from marine habitat conservation to applied science. In recent years, advances in techniques in interdisciplinary research fields, including metabolic engineering and synthetic biology have significantly improved the production of marine-derived commodities. In this review, we outline the recent progress in the use or marine enzymes and molecules in biotechnology, including newly discovered products, function optimization of enzymes, and production improvement of small molecules.

Efficient control of acrylamide in French fries by an extraordinarily active and thermo-stable l-asparaginase: A lab-scale study

As a potential carcinogen, acrylamide (AA) widely exists in starch-rich foods during frying, triggering international health alerts. l-Asparaginase (l-ASNase, EC 3.5.1.1) could efficiently inhibit the AA by hydrolyzing its precursor l-Asparagine. Here, a novel recombinant l-ASNase from Palaeococcus ferrophilus was identified for the first time. The purified enzyme exhibited its highest activity at pH 8.5 and 95 °C and retained more than 70% relative activity after incubation at 80 °C for 2 h. Compared to untreated French fries, the AA content in the enzyme-treated (10 U/mL, 85 °C, 15 min) French fries was significantly reduced by 79%. Notably, the l-ASNase could remain over 98% of initial activity after three months of storage at 4 °C, suggesting good storage stability. These results demonstrated that P. ferrophilusl-ASNase could be a great candidate in controlling AA in the food industry, especially at high blanching temperature.

Characteristics of French Fries and Potato Chips in Aspect of Acrylamide Content—Methods of Reducing the Toxic Compound Content in Ready Potato Snacks

The reduction of toxic acrylamide content in potato snacks, i.e., French fries and potato chips, is necessary due to the adverse effects of this compound on the human body. Therefore, in the presented review paper, a detailed characterization of French fries and chips in terms of AA content and their organoleptic quality is included. Detailed information was also collected on the raw material and technological factors that affect the formation of acrylamide content, including methods and techniques affecting the reduction of the amount of this compound in potato snacks. The obligation to control the level of acrylamide in various food products (including fried potato snacks with a higher content of this compound), introduced in 2018, has mobilized manufacturers to seek solutions, while scientists conduct further intensive research on the possibility of reducing the level of AA or even eliminating its presence from products. Therefore, it is necessary to conduct such activities, especially, because potato French fries and potato chips are willingly consumed by younger and younger consumers.

Non-classical secretion of a type I L-asparaginase in Bacillus subtilis

L-asparaginase (EC 3.5.1.1) showed great commercial value owing to its effective treatment of acute lymphoblastic leukemia (ALL), lymphoid system malignancies and Hodgkin disease, and also to its use in the prevention of acrylamide formation in fried and baked foods. In this study, a type I L-asparaginase gene from Bacillus licheniformis Z-1 (BlAase) was cloned and expressed in Bacillus subtilis RIK 1285. Results showed that even without the mediation of any N-terminal signal peptides, BlAase can efficiently secrete into the medium. Further investigation indicated that the secretion of the BlAase was via neither Sec- nor Tat-dependent secretion pathway, and both the N- and C-terminal regions of the BlAase were essential for its expression and secretion, implying that BlAase might be secreted via a non-classical secretion pathway. To explore its secretion ability, BlAase was used as a signal peptide to direct the secretion of various heterologous proteins, where two of five proteins were successfully secreted with the mediation of BlAase. To the best of our knowledge, this is the first time to achieve extracellular expression of L-asparaginase via non-classical protein secretion pathway in B. subtilis, and provide a potential tool for secretion of recombinant proteins expressed in B. subtilis using BlAase as a signal peptide.

Structures of l-asparaginase from Bacillus licheniformis Reveal an Essential Residue for its Substrate Stereoselectivity

l-Asparaginase, which catalyzes the hydrolysis of l-asparagine, is an important enzyme in both the clinical and food industry. Exploration of efficient l-asparaginase with high substrate specificity, especially high chiral selectivity, is essential for extending its use. Herein, various crystal structures of type I l-asparaginase from Bacillus licheniformis (BlAsnase) have been resolved, and we found that there are two additional tyrosines in BlAsnase, contributing to the binding and catalysis of d-asparagine. Strikingly, the substitution of Tyr278 with methionine impaired the interaction with d-asparagine via water molecules due to the small hydrophobic side chain of methionine, which forced the ligand to the deep side of the active site toward the catalytic residues and thus resulted in the loss of hydrolyzing function. Our investigation of the substrate recognition mechanism of BlAsnase is significant for both a better understanding of l-asparaginase and its rational design to achieve high specificity for clinical and industrial applications.

Surface Modification of 316L SS Implants by Applying Bioglass/Gelatin/Polycaprolactone Composite Coatings for Biomedical Applications

In this study, various composites of bioglass/gelatin/polycaprolactone (BG/GE/PCL) were produced and coated on the surface of 316L stainless steel (SS) to improve its bioactivity. X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were utilized to characterize the specimens. The results showed that bioglass particles were distributed uniformly in the coating. By increasing the wt.% of bioglass in the nanocomposite coatings, the surface roughness and adhesion strength increased. The corrosion behavior of GE/PCL (PCL-10 wt.% gelatin coated on 316L SS) and 3BG/GE/PCL (GE/PCL including 3 wt.% bioglass coated on 316L SS) samples were studied in PBS solution. The results demonstrated that 3BG/GE/PCL sample improved the corrosion resistance drastically compared to the GE/PCL specimen. In vitro bioactivity of samples was examined after soaking the specimens for 7, 14 and 28 days in simulated body fluid (SBF). The results showed a significant apatite formation on the surface of 3BG/GE/PCL samples. The cell viability evaluation was performed using 3- (4, 5-dimethylthiazol-2-yl)-2,5 diphenyltetrazoliumbromide (MTT) tests which confirmed the enhanced cell viability on the surface of 3BG/GE/PCL samples. The in vivo behavior of specimens illustrated no toxicity and inflammatory response and was in a good agreement with the results obtained from the in vitro test.

Spirulina maxima L-asparaginase: Immobilization, Antiviral and Antiproliferation Activities

BACKGROUND

L-asparaginase (L-AsnA) enzyme has gained significant attention in the food, biocatalysts and pharmaceutics industry. It (L-AsnA) has been widely used in food processing industries as a promising acrylamide mitigating agent and as a therapeutic agent in the treatment of certain human cancers.

OBJECTIVE

Based on US Patent (4,433,054; 1984), L-asparaginase (L-AsnA) enzyme is immobilized by admixing the active enzyme on the polysaccharide to be in a gel form. The storage stability of immobilized L-AsnA enzyme and its anti-proliferation and antiviral activity were determined.

METHODS

In the present study, S. maxima was cultured at large scales (300 liter) for the production of enough extracellular L-asparaginase (L-AsnA) using modified (high N concentration) Zarrouk medium as we reported in a previous study. L-AsnA was immobilized on natural polymers, as agar cake beads, agarose pieces and gelatin blocks, in order to evaluate the efficiency of physical entrapment techniques. Anti-proliferation properties of L-AsnA against lung carcinoma A549, hepatocellular carcinoma Hep-G2 and prostate carcinoma PC3 human cancer cell lines were assessed by the MTT cell viability method. In addition, the antiviral activity against Coxsackie B3 (CSB3) Virus was assessed.

RESULTS

The highest L-AsnA immobilized activity and immobilization yield were achieved with agar cakes bead. The purified S. maxima L-AsnA showed good antiviral activity against Coxsackie B3 (CSB3) Virus in a dose-dependent manner with an IC50 value 17.03 μg/ml. The antiviral mode of action is presumably due to their capability of inhibiting attachment, blocking the adsorption and penetration event of the viral replication cycle with 89.24%, 72.78% and 72.78%, respectively. Also, S. maxima L-AsnA showed anti-proliferation effect against lung carcinoma A549, hepatocellular carcinoma Hep-G2 and prostate carcinoma PC3 human cancer cell lines, with an IC50 of 22.54, 24.65 and 56.61 μg/ml, respectively.

CONCLUSION

It is interesting to favor L-asparaginase of S. maxima which showed antiviral activity and anti-proliferation effect against different types of human cell lines. Thus, S. maxima microalgae might be a good source for L-AsnA enzymes and can be immobilized on natural polymers.

Development and characterization of a novel l-asparaginase/MWCNT nanobioconjugate

The enzyme l-asparaginase (ASNase) presents effective antineoplastic properties used for acute lymphoblastic leukemia treatment besides their potential use in the food sector to decrease the acrylamide formation. Considering their applications, the improvement of this enzyme's properties by efficient immobilization techniques is in high demand. Carbon nanotubes are promising enzyme immobilization supports, since these materials have increased surface area and effective capacity for enzyme loading. Accordingly, in this study, multi-walled carbon nanotubes (MWCNTs) were explored as novel supports for ASNase immobilization by a simple adsorption method. The effect of pH and contact time of immobilization, as well as the ASNase to nanoparticles mass ratio, were optimized according to the enzyme immobilization yield and relative recovered activity. The enzyme–MWCNTs bioconjugation was confirmed by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Raman and transmission electron microscopy (TEM) studies. MWCNTs have a high ASNase loading capacity, with a maximum immobilization yield of 90%. The adsorbed ASNase retains 90% of the initial enzyme activity at the optimized conditions (pH 8.0, 60 min, and 1.5 × 10⁻³ g mL⁻¹ of ASNase). According to these results, ASNase immobilized onto MWCNTs can find improved applications in several areas, namely biosensors, medicine and food industry.

l-Asparaginase immobilization by adsorption over MWCNTs for potential application in pharmaceutical and food industries.

Antitumor activity and ability to prevent acrylamide formation in fried foods of asparaginase from soybean root nodules

A novel asparaginase (designated srnASNase) has been purified from soybean root nodules and identified by MALDI-TOF/TOF-MS. And the enzymatic properties, antitumor activity and the ability to prevent acrylamide formation in fried foods of srnASNase were evaluated. SrnASNase had high specific activity (531.37 U/mg) toward L-asparagine under optimum conditions (pH 8.0 and 40°C), no activity toward L-glutamine and D-glutamine, but trace activity toward D-asparagine. It was stable in the pH range of 7.0-9.0 and up to 40°C. The Km and Vmax of srnASNase were 0.36 mM and 51.64 mM/min, respectively. Further, in vitro anti-proliferative activity on human cancer cells assay showed that srnASNase was superior to commercial asparaginase in solution by controlling the tumor cell growth with time. In addition, srnASNase showed more effective acrylamide mitigation than commercial asparaginase in fried foods. These results indicate that srnASNase is a potential candidate for applications in the food processing and pharmaceutical industry. PRACTICAL APPLICATIONS: L-asparaginase (L-asparagine amidohydrolase; EC 3.5.1.1) is an enzyme that catalyzes the hydrolysis of the amide group of the side-chain of L-asparagine into aspartic acid and ammonia. It has long been used as a primary component in the treatment of acute lymphoblastic leukemia (All) and other related blood cancers. Apart from its clinical usage, L-asparaginase has attracted more attention in the food processing industries as a promising acrylamide-mitigating agent in recent years. This research revealed that soybean root nodules might be good sources of novel asparaginase.

Production and structural modeling of a novel asparaginase in Yarrowia lipolytica

Asparaginase catalyzes the conversion of asparagine into aspartic acid and ammonia. The enzyme has various industrial applications and it is considered as an anticancer drug for treatment of certain leukemias. In the current study, production of asparaginase was investigated by Yarrowia lipolytica as well as optimized its production and determined its molecular characteristics by in silico analysis. Y. lipolytica DSM3286 produced 17.14 U/ml of asparaginase in flask culture. Optimization of asparaginase production was done by response surface methodology and the enzyme production increases up to 102.85 U/ml. The enzyme production reached 210 U/ml in a bioreactor which is 12-fold more than flask culture containing non-optimized medium. Asparaginase gene of Y. lipolytica was identified and isolated on the basis of comparison with asparaginase gene sequences of other microorganisms. The gene has 981 nucleotides and its protein has 326 amino acids. According to in silico analysis, the secondary structure of the enzyme is composed of 9 α-helixes and 11 β-sheets. Y. lipolytica produces type II asparaginase with high affinity for asparagine which is a suitable eukaryotic asparaginase for treatment of hematopoietic cancers. Hence, Y. lipolytica could be recommended as a new eukaryotic microbial source for the production of this important therapeutic enzyme.

Marine microbial L-asparaginase: Biochemistry, molecular approaches and applications in tumor therapy and in food industry

The marine environment is a rich source of biological and chemical diversity. It covers more than 70% of the Earth's surface and features a wide diversity of habitats, often displaying extreme conditions, where marine organisms thrive, offering a vast pool for microorganisms and enzymes. Given the dissimilarity between marine and terrestrial habitats, enzymes and microorganisms, either novel or with different and appealing features as compared to terrestrial counterparts, may be identified and isolated. L-asparaginase (E.C. 3.5.1.1), is among the relevant enzymes that can be obtained from marine sources. This amidohydrolase acts on L-asparagine and produce L-aspartate and ammonia, accordingly it has an acknowledged chemotherapeutic application, namely in acute lymphoblastic leukemia. Moreover, L-asparaginase is also of interest in the food industry as it prevents acrylamide formation. Terrestrial organisms have been largely tapped for L-asparaginases, but most failed to comply with criteria for practical applications, whereas marine sources have only been marginally screened. This work provides an overview on the relevant features of this enzyme and the framework for its application, with a clear emphasis on the use of L-asparaginase from marine sources. The review envisages to highlight the unique properties of marine L-asparaginases that could make them good candidates for medical applications and industries, especially in food safety.