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.

Production, characterization and techno-economic evaluation of Aspergillus fusant L-asparaginase

Protoplast fusion is one of the most reliable methods of introducing desirable traits into industrially-promising fungal strains. It harnesses the entire genomic repertoire of fusing microorganisms by routing the natural barrier and genetic incompatibility between them. In the present study, the axenic culture of a thermo-halotolerant strain of Aspergillus candidus (Asp-C) produced an anti-leukemic L-asparaginase (L-ASNase) while a xylan-degrading strain of Aspergillus sydowii (Asp-S) produced the acrylamide-reduction type. Protoplast fusion of the wild strains generated Fusant-06 with improved anti-leukemic and acrylamide reduction potentials. Submerged fed-batch fermentation was preferred to batch and continuous modes on the basis of impressive techno-economics. Fusant-06 L-ASNase was purified by PEG/Na⁺ citrate aqueous two-phase system (ATPS) to 146.21-fold and global sensitivity analysis report revealed polymer molecular weight and citrate concentration as major determinants of yield and purification factor, respectively. The enzyme was characterized by molecular weight, amino acid profile, activity and stability to chemical agents. Michaelis-Menten kinetics, evaluated under optimum conditions gave K_m, V_max, K_cat, and K_cat/K_m as 6.67 × 10^-5 M, 1666.67 µmolmin^-1 mg^-1 protein, 3.88 × 10⁴ min^-1 and 5.81 × 10⁸ M^-1.min^-1 respectively. In-vitro cytotoxicity of HL-60 cell lines by Fusant-06 L-ASNase improved significantly from their respective wild strains. Stability of Fusant-06 L-ASNase over a wide range of pH, temperature and NaCl concentration, coupled with its micromolar K_m value, confers commercial and therapeutic value on the product. Free-radical scavenging and acrylamide reduction activities were intermediate and the conferred thermo-halo-stability could be exploited for sustainable clinical and food industry applications.

Interspecific protoplast fusion of atmospheric and room-temperature plasma mutants of Aspergillus generates an L-asparaginase hyper-producing hybrid with techno-economic benefits

The axenic culture of Aspergillus candidus (Asp-C) produced an anti-leukemic L-asparaginase while Aspergillus sydowii (Asp-S) produced the acrylamide-reduction type. Upon mutagenesis by atmospheric and room-temperature plasma (ARTP), their individual L-asparaginase activities improved 2.3-folds in each of Ile^-Thr^-Asp-C-180-K and Val^-Asp-S-180-E stable mutants. Protoplast fusion of selected stable mutants generated fusant-09 with improved anti-leukemic activity, acrylamide reduction, higher temperature optimum and superior kinetic parameters. Submerged (SmF) and solid-state fermentation (SSF) types were compared; likewise batch, fed-batch and continuous fermentation modes; and fed-batch submerged fermentation was selected on the basis of impressive techno-economics. Fusant L-asparaginase was purified by PEG/Na⁺ citrate aqueous two-phase system and molecular exclusion chromatography to 69.96 and 146.21-fold, respectively, and characterized by molecular weight, specificity, activity and stability to chemical and physical agents. Michaelis-Menten kinetics, evaluated under optimum conditions gave K_m, V_max, K_cat, and K_cat/K_m as 1.667 × 10^-3 M, 1666.67 µmol min^-1 mg^-1 protein, 645.99 s^-1 and 3.88 × 10⁵ M^-1 s^-1 respectively. In-vitro cytotoxicity of HL-60 cell lines by fusant-09 L-asparaginase improved 3.00 and 18.71-folds from mutants Ile^-Thr^-Asp-C-180-K and Val^-Asp-S-180-E, and from 5.73 and 32.55 from respective original strains. Free-radical scavenging and acrylamide reduction improvements were intermediate. Fusant-09 L-asparaginase is strongly recommended for sustainable economic anti-leukemic and food industry applications.