Characterization of Penicillium crustosum L-asparaginase and its acrylamide alleviation efficiency in roasted coffee beans at non-cytotoxic levels

Recent advances in L-Asparaginase enzyme production and formulation development for acrylamide reduction during food processing

L-asparagine is an essential amino acid for cell growth and common constituent of all the proteins. During high temperature food processing it reacts with reducing sugars and leads to acrylamide production through a complex process known as Maillard reaction. L-asparaginase hydrolyses the amine-group of L-asparagine to produce aspartic acid and ammonia. L-asparaginase pre-treatment of potato led to more than 80 % reduction of acrylamide content in foods like french fries, potato chips and in flour-dough based products. New cost-effective strategies for large scale L-asparaginase production and diverse types of formulations will be needed to successfully integrate L-asparaginase in food processing. Here we comprehensively review the recent developments in enzyme production to enhance the yield, activity and specificity of L-asparaginase. Novel liquid and lyophilized formulations are developed to enhance stability and activity of the enzyme under different conditions. These developments present a promising approach to enzymatically mitigate acrylamide formation during food processing.

Production and immobilization of pectinases from Penicillium crustosum in magnetic core-shell nanostructures for juice clarification

Global market of food enzymes is held by pectinases, mostly sourced from filamentous fungi via submerged fermentation. Given the one-time use nature of enzymes to clarify juices and wines, there is a crucial need to explore alternatives for enzyme immobilization, enabling their reuse in food applications. In this research, an isolated fungal strain (Penicillium crustosum OR889307) was evaluated as a new potential pectinase producer in submerged fermentation. Additionally, the enzyme was immobilized in magnetic core-shell nanostructures for juice clarification. Findings revealed that Penicillium crustosum exhibited enzymatic activities higher than other Penicillium species, and pectinase production was enhanced with lemon peel as a cosubstrate in submerged fermentation. The enzyme production (548.93 U/mL) was optimized by response surface methodology, determining the optimal conditions at 35 °C and pH 6.0. Subsequently, the enzyme was covalently immobilized on synthesized magnetic core-shell nanoparticles. The immobilized enzyme exhibited superior stability at higher temperatures (50 °C) and acidic conditions (pH 4.5). Finally, the immobilized pectinases decreased 30 % the orange juice turbidity and maintained 84 % of the enzymatic activity after five consecutive cycles. In conclusion, Penicillium crustosum is a proven pectinase producer and these enzymes immobilized on functionalized nanoparticles improve the stability and reusability of pectinase for juice clarification.

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.

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.

Strain improvement, artificial intelligence optimization, and sensitivity analysis of asparaginase-mediated acrylamide reduction in sweet potato chips

In recent times, L-asparaginase has emerged as a potential anti-carcinogen through hydrolysis of L-asparagine in the blood for anti-leukemic application, and in carbohydrate-based foods, for acrylamide reduction applications. In this study, Aspergillus sydowii strain UCCM 00124 produced an L-asparaginase with a baseline acrylamide reduction potential of 64.5% in sweet potato chips. Plasma mutagenesis at atmospheric pressure and room temperature (ARTP) was employed to improve L-asparaginase production while artificial neural network embedded with genetic algorithm (ANN-GA) and global sensitivity analysis were used to identify and optimize process conditions for improved acrylamide reduction in sweet potato chips. The ARTP mutagenesis generated a valine-deficient mutant, Val-Asp-S-180-L with 2.5-fold L-asparaginase improvement. The ANN-GA hybrid evolutionary intelligence significantly improved process efficiency to 98.18% under optimized conditions set as 118.6 °C, 726.37 g/L asparagine content, 9.92 µg/mL L-asparaginase, 4.54% NaCl, and soaking time of 15 h without significant changes in sensory properties. The sensitivity index revealed initial asparagine content as the most sensitive parameter to the bioprocess. The enzyme demonstrated significant thermo-stability with Arrhenius deactivation rate constant, Kd, of 0.00562 min-1 and half-life, t1/2, of 123.35 min at 338 K. These conditions are recommended for sustainable healthier, and safer sweet potato chips processing in the food industry.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05757-5.

Response surface methodology based optimized production, purification, and characterization of L-asparaginase from Fusarium foetens

L-asparaginase is used as one of the prime chemotherapeutic agents to treat acute lymphoblastic leukemia. L-asparaginase obtained from bacteria exhibits hypersensitive reactions including various side effects. The present work aimed to optimize growth parameters for maximum production of L-asparaginase by Fusarium foetens through response surface methodology, its purification, and characterization. The optimization of L-asparaginase production by Fusarium foetens was initially done through a one-factor-at-a-time method. L-asparaginase production was further optimized using a central composite design based response surface methodology. The maximum L-asparaginase activity of 12.83 IU/ml was obtained under the following growth conditions; temperature-27.5 °C, pH-8, inoculum concentration-1.5 × 10⁶ spores/ml, and incubation period-7 days. In comparison with the unoptimized growth conditions (4.58 IU/ml), the optimization led to a 2.65-fold increase in the L-asparaginase activity. The L-asparaginase from Fusarium foetens was purified 15.60-fold, with a yield of 39.89% using DEAE-cellulose column chromatography. After purification, the L-asparaginase activity was determined to be 127.26 IU/ml and the specific activity was found to be 231.38 IU/mg. The molecular mass was estimated to be approximately 37 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme showed optimum activity at pH 5, and a temperature of 40 °C. The enzyme showed 100% specificity towards L-asparagine and no activity towards L-glutamine. Its activity was enhanced by Mn²⁺, Fe²⁺, and Mg², while it was inhibited by β-mercaptoethanol and EDTA. The Km and Vmax of the purified L-asparaginase were found to be 23.82 mM and 210.3 IU/ml respectively. The results suggest that Fusarium foetens could be a potent candidate for the bioprocessing of L-asparaginase at a large scale.

Construction of L-Asparaginase Stable Mutation for the Application in Food Acrylamide Mitigation

Acrylamide, a II A carcinogen, widely exists in fried and baked foods. L-asparaginase can inhibit acrylamide formation in foods, and enzymatic stability is the key to its application. In this study, the Escherichia coli L-asparaginase (ECA) stable variant, D60W/L211R/L310R, was obtained with molecular dynamics (MD) simulation, saturation mutation, and combinatorial mutation, the half-life of which increased to 110 min from 60 min at 50 °C. Furthermore, the working temperature (maintaining the activity above 80%) of mutation expanded from 31 °C–43 °C to 35 °C–55 °C, and the relative activity of mutation increased to 82% from 65% at a pH range of 6–10. On treating 60 U/mL and 100 U/g flour L-asparaginase stable mutant (D60W/L211R/L310R) under uncontrolled temperature and pH, the acrylamide content of potato chips and bread was reduced by 66.9% and 51.7%, which was 27% and 49.9% higher than that of the wild type, respectively. These results demonstrated that the mutation could be of great potential to reduce food acrylamide formation in practical applications.

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.