Valorization of fish processing by-products through combined enzymatic and microbial hydrolysis: nitrogen recovery and fertilizer efficiency in wheat
Tamara Solís, Silvana Valdivia, Alejandra Vergara, Marcela Carvajal +2
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75% confidenceThis study investigates the sustainable valorization of fish processing by-products through combined enzymatic and microbial hydrolysis to produce nitrogen-rich fertilizers for wheat. The research demonstrates that a synergistic combination of Alcalase enzymatic treatment and lactic acid bacterial fermentation significantly enhances protein recovery and alpha-amino group concentration compared to single-process methods. These optimized hydrolysates were subsequently evaluated as effective nitrogen sources under controlled growth conditions.
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Abstract
The bioconversion of fish by-products has been evidenced as a sustainable process to convert food waste into high-value products. In the present study, protein hydrolysates were produced from fish by-products by different bioprocesses and evaluated as fertilizers in wheat ( Triticum aestivum L. ) on a nitrogen-equivalent basis. Fish by-products were processed through grinding prior to bioconversion. Enzymatic hydrolysis was performed using Alcalase at 55 °C, pH 6.5, and a 3-h reaction, while microbial conversion was assessed using a lactic culture at 40 °C, pH 6.5, and a 10-day culture. Hydrolysates obtained by enzymatic and microbial bioconversion were evaluated as fertilizers by adding 30 mg after 7 and 14 days to wheat seeds sown under controlled conditions. Protease and microbial hydrolysis generated high concentrations of α -amino groups, yielding 100 mM and 170 mM, respectively. The combined process exhibited a synergistic effect, yielding 226 mM of α -amino groups and 33% of protein recovery. Plant growth assays were conducted under controlled conditions using nitrogen-equivalent doses of each hydrolysate. Microbial and combined enzymatic-microbial hydrolysates generated average plant lengths of 52 cm and 54 cm compared to 44 cm in the control, while plant biomass reached 1.7 g and 2.3 g with microbial and combined enzymatic-microbial hydrolysates compared to 0.7 g in the control. Photosynthetic parameters remained within normal physiological ranges from 2.5 to 3.3 for performance index (PI) and from 0.78 to 0.80 for maximum quantum efficiency (Fv/Fm). The integration of enzymatic and microbial catalysis produced the most effective biostimulant activity, highlighting the value of combining enzymatic specificity with microbial metabolic versatility. These findings support fish-derived protein hydrolysates as efficient and eco-friendly fertilizers that are capable of improving plant growth while contributing to sustainable and integral utilization of natural resources.
Key findings
- Enzymatic hydrolysis using Alcalase yielded 100 mM of alpha-amino groups, while microbial conversion using lactic culture achieved 170 mM.
- The combined enzymatic and microbial process exhibited a synergistic effect, resulting in the highest yield of 226 mM alpha-amino groups and 33% protein recovery.
- Fish by-product hydrolysates produced via these bioprocesses function effectively as nitrogen-equivalent fertilizers for wheat cultivation.
Keywords
Identifiers
- Journal
- Frontiers in Nutrition
- Year
- 2026