Single Cell Protein Production from Tomato Leaves and Stems by Submerged Fermentation

Date

2026-1

Author

Menteş, Duygu

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Despite being rich in carbohydrates and proteins, large quantities of tomato leaves and stems are typically discarded as waste after harvesting. However, their high availability and reducing sugar potential make these residues promising raw materials for producing value-added substrates to be used in fermentation applications. The aim of this study was to produce single cell protein (SCP) with high protein content from tomato leaves and stems using Saccharomyces cerevisiae via submerged fermentation in a bioreactor. They were subjected to different pretreatments followed by enzymatic hydrolysis to obtain a fermentation medium enriched in reducing sugars which was measured using DNS method. Naturally occurring glycoalkaloids (α-tomatine and solanine) were eliminated from the prepared substrates. Fermentation experiments were carried out in a 2 L bioreactor under varying agitation speeds (100, 200, and 300 rpm), inoculum sizes (1%, 3%, and 5% v/v), and fermentation times (24, 72, and 120 h). The maximum biomass yield, corresponding to 2.76 g/L of protein, was obtained at an agitation speed of 300 rpm with a 5% inoculum after 120 h of fermentation. The SCP contained 39.75% protein, as determined by the Kjeldahl method, representing approximately a fourfold increase compared to the protein content of untreated tomato residues. Amino acid profiling by LC–MS/MS revealed the presence of essential amino acids, including L-threonine, L-leucine, L-isoleucine, and L-lysine. The highest protein release from microbial cells (26.87%) was achieved following high-pressure homogenization at 1500 bar for 11 passes. This study demonstrates the feasibility of converting tomato leaves and stems into nutritionally valuable SCP and highlights fermentation as an effective strategy for valorizing agricultural residues within a circular bioeconomy framework.

Subject Keywords

Single cell protein, Tomato leaves, Saccharomyces cerevisiae, Submerged fermentation, Amino acid

URI

https://hdl.handle.net/11511/118408

Collections

Graduate School of Natural and Applied Sciences, Thesis