Browsing by Subject "Enzymatic hydrolysis"

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Application of AprX from Pseudomonas paralactis for the improvement of the emulsifying properties of milk, plant and insect protein and estimation of their hydrolysate’s bitter potential
(2025) Volk, Veronika; Ewert, Jacob; Longhi, Miriam; Stressler, Timo; Fischer, Lutz
Protein properties can be modified by selective enzymatic hydrolysis. In this study, the alkaline metalloendopeptidase AprX (Serralysin; EC 3.4.24.40) from Pseudomonas paralactis was used for the tailored hydrolysis of different food proteins resulting in the production of protein hydrolysates with improved emulsifying properties. Sodium caseinate, wheat gluten and buffalo worm protein were used for AprX hydrolysis at 40 °C and pH 8 to cover a spectrum of different protein sources. A maximum degree of hydrolysis (DH) of 13.1 ± 0.2%, 14.2 ± 0.1% and 20.7 ± 0.1% was reached for sodium caseinate, wheat gluten and the worm protein, respectively. The corresponding hydrolysate properties were analyzed regarding their particle size, peptide composition, solubility, viscosity, surface hydrophobicity and interfacial tension. The emulsifying properties were investigated by the oil-droplet size, ζ-potential and stability of emulsions prepared from the hydrolysates. Using partially hydrolyzed sodium caseinate (DH = 10.6%) as an emulsifier lead to an eightfold increase of the emulsion stability (t1/2 = 180 ± 0 min) compared to unhydrolyzed sodium caseinate. The emulsion stability using wheat gluten hydrolysates (DH = 11.9%) was increased 30-fold (t1/2 = 45 ± 5 min). Simultaneously, the solubility of gluten was increased by 60%. Buffalo worm hydrolysates (DH = 14.6%) had a twofold (t1/2 = 85 ± 5 min) increased emulsion stability. In conclusion, AprX can be used to improve the solubility and emulsifying properties of food proteins at a relatively high DH.
Hydrolyzable microplastics in soil-low biodegradation but formation of a specific microbial habitat?
(2022) Schöpfer, Lion; Schnepf, Uwe; Marhan, Sven; Brümmer, Franz; Kandeler, Ellen; Pagel, Holger
Microplastics (MP, plastic particles between 0.1 and 5000 μm) contaminate agricultural soils through the application of organic fertilizers, sewage sludge, and plastic mulch. MP surfaces and the MP-soil interface provide specific habitats for soil microorganisms—the plastisphere. Microorganisms in the plastisphere may benefit from utilizing MP as a carbon (C) source. Hydrolyzable MP with ester bonds are susceptible to enzymatic depolymerization by hydrolysis. In a microcosm experiment, we investigated MP biodegradation of small and large (< 0.5 mm and 0.5–2 mm respectively), hydrolyzable (a poly(lactic acid)/poly(butylene co-adipate terephthalate) blend, PLA/PBAT) and non-hydrolyzable (low-density polyethylene, LDPE) polymers, and the effects of these MP on microorganisms in dry and wet MP-amended soil. MP affected neither abundance and composition of the main soil microbial groups (fungi, Gram-negative, and Gram-positive bacteria), specific activities of ß-glucosidase, ß-xylosidase, lipase, and phenoloxidase, nor respiration in MP-amended soil. Only large PLA/PBAT particles in dry soil were significantly mineralized (15.4% of initial PLA/PBAT-C after 230 days). PLA/PBAT mineralization coincided with enhanced lipase and ß-glucosidase activities on the surfaces of individual PLA/PBAT particles extracted from the soil after incubation (compared to LDPE and non-incubated PLA/PBAT particles). We detected cracks on the surfaces of PLA/PBAT particles using scanning electron microscopy, indicating initiation of MP biodegradation, presumably due to depolymerization by lipases. Results suggest that the PLA/PBAT plastisphere is a polymer-specific habitat for lipase-producing soil microorganisms. Our study demonstrates that analyzing biogeochemical interactions within polymer-specific plastispheres is essential to assess MP fate and their impacts on microbially driven soil processes.
Impact of particle size reduction on high gravity enzymatic hydrolysis of steam-exploded wheat straw
(2021) Hoppert, Luis; Einfalt, Daniel
Economically feasible bioethanol production from lignocellulosic biomass requires solid loadings ≥ 15% dry matter (DM, w/w). However, increased solid loadings can lead to process difficulties, which are characterized by high apparent slurry viscosity, insufficient substrate mixing and limited water availability, resulting in reduced final glucose yields. To overcome these limitations, this study focused on enzymatic hydrolysis of 10–35% DM solid loadings with steam-exploded wheat straw in two different particle sizes. At solid loadings of 20 and 25% DM small particle size of ≤ 2.5 mm yielded 16.9 ± 1.1% and 10.2 ± 1.4% increased final glucose concentrations compared to large particle size of 30 ± 20 mm. Small particle size also positively influenced slurry viscosity and, therefore, miscibility. As a key finding of this investigation, high gravity enzymatic hydrolysis with solid loadings of 30–35% DM was indeed successfully employed when wheat straw was applied in small particle size. Here, the highest final glucose yield was achieved with 127.9 ± 4.9 g L⁻¹ at 35% DM solid loading. An increase in the solid loading from 10 to 35% DM in small particle size experiments resulted in a 460% increase in the final glucose concentration.