Protein hydrolysates from residues of mustelus schmitti as peptones for growth carotenogenic native yeast rhodotorula glutinis

ARRUEBARRENA DI PALMA, ANDRÉS; TURINA, SOLEDAD YANINA; ISLA NAVEIRA, ROCÍO; PEREYRA, CINTIA

Chapadmalal

Congreso; XVIII Congreso de la sociedad Argentina de Microbiología General; 2023

Sociedad Argentina de Microbiología General

The fish production industry is experiencing significant growth, with a projected processing volume of over 196 million tons by 2025. This expansion also results in substantial quantities of waste, including heads, skin, trimmings, viscera, frames, and occasionally muscle. This underutilized biomass contains a large quantity of proteins and effective strategies to utilize them are needed. Fish protein hydrolysates (FPH) technology consists in treating by-products biomass with protease enzymes to obtain an aqueous fraction enriched in oligopeptides and free aminoacids. The FPH could be used as a valuable nitrogen source and peptone in several applications. The use of this nitrogen source to grow technologically important microorganisms could reduce the cost associated with biomass generation and/or production of relevant microbial by products. On the other hand, carotenoids, compounds with diverse applications in industry, medicine and agriculture can be obtained through microbiological synthesis. However the production of natural carotenoids is more expensive compared to their synthetic counterparts. In this work we studied the production of FPH from residues of Mustelus schmitti, a cartilaginous species commercially used in Argentina. We analyzed kinetics of hydrolysis by pHstat method, oligopeptide and free aminoacids obtention by SDS PAGE and HPLC, and the potential use of FPH for growth of a native yeast Rhodotorula glutinis isolated from native plants that produce carotenes. Yeast growth was determined (cell/ml) and the carotenes extracted from yeast biomass were identified by TLC and quantified by UV-visible spectroscopy. Enzymatic hydrolysis (Alcalase) of M. schmitti residues shows a degree of 45% upon 1 h of treatment and SDS-PAGE indicated extensive degradation of initial protein content. Free aminoacids content increased 2-3 folds for all aminoacids, except for tyrosine which was gradually degraded at the end of the hydrolysis. Soluble protein and oligopeptide quantification of FPH indicated a concentration of 40 mg/ml, 4 fold higher than contained in standard laboratory yeast medium (YPD, 10 mg/ml). Standard YPD medium or FPH supplemented with glucose as a carbon source was used to grow R. glutinis (both mediums with protein concentration adjusted to 10 mg/ml). In both cases, yeast grew equally (4x108 cell/ml in both cases) and produced carotenes. These were extracted and run on TLC plates indicating that this native yeast produces β-carotene, tolurene and torularhodin as main carotenoids. Quantification of total carotenes as β carotene equivalents, shows that yeast produces at equal level these compounds in both types of medium. All together these results show that from residues of processing fish and enzymatic hydrolysis, we obtain oligopeptides and free amino acids that support carotenogenic yeast growth, making possible the bioproduction of carotenoids, important molecules with many technological applications.