Production of L-carnitine-enriched edible filamentous fungal biomass through submerged cultivation

Abstract

The edible filamentous fungi are hot candidate for future supply of functional food and feed with e.g. protein, essential amino acids, and compounds with immunostimulant activity. L-carnitine that plays a crucial role in energy metabolism represents a functional compound normally produced by Zygomycetes filamentous fungus Rhizopus oligosporus in solid-state fermentation. The present study provides the first insights on production of L-carnitine-enriched edible fungal biomass through submerged cultivation of several Ascomycetes and Zygomycetes including Aspergillus oryzae, Neurospora intermedia, Rhizopus oryzae, and Rhizopus oligosporus. A. oryzae with 3 mg L-carnitine yield per gram of fungal biomass, indicates great potential on production of this bioactive compound which is remarkably higher than the other tested fungi in this work and also previous studies. In addition to fungal strain, other factors such as cultivation time and presence of yeast extract were found to play a role. Further studies on submerged growth optimization of A. oryzae in both high-quality recipes and in medium based on low-value substrates are proposed in order to clarify its potential for production of L-carnitine-enriched fungal biomass.

Comparative Analysis of L-Carnitine Production by Y. Lipolytica in Different Culture Conditions in Biofuel Waste and Fatty-Poor Medium for Commercial Purposes

“…In the present study, we examined the effect of the culture conditions, two different media, and supplementation of the media on the level of free L-carnitine in the biomass of Y. lipolytica strains. The results con rm other ndings [7,22,[35][36][37][38] revealing that the fermentation process parameters can have a signi cant impact on improvement of the nutrient content in the biomass of the studied yeast strains. However, we showed that the concentration of free L-carnitine in the yeast biomass depended primarily on the medium used, and, to some extent, on the strains and culture conditions.…”

“…The standard laboratory YPD medium, used in this study as supplementary, contains yeast extract with only 0.10%-0.15% of fatty acids. Yeast extract is mainly added to the medium as a nitrogen source; however, it also contains several biocomponents, including su cient amounts of carnitine, to complement the carnitine requirements of yeast [4,7]. It was reported that the effect of yeast extract on Lcarnitine biosynthesis was dissimilar among tested fungal strains.…”

“…The best-known yeast Saccharomyces cerevisiae is unable to synthesize L-carnitine. However, this yeast possesses enzymatic activities, especially CATs, which allow the uptake of L-carnitine from the environment [4,7,10]. Studies reported elsewhere [3,[12][13][14] revealed that some oleaginous yeast, e.g.…”

“…CATs transfer the coenzyme A (CoA) group of acetyl-CoA to carnitine; hence, acetyl-carnitine is biosynthesized, which can be transferred via the peroxisomal and mitochondrial membranes to the tricarboxylic acid (TCA) cycle [7]. Interestingly, the supplementation with L-carnitine results in more effective fatty acids transport to the mitochondria, where their decomposition occurs in the β-oxidation process [8].…”

“…They play the sole role in β-oxidation in the fatty acid degradation process causing the formation of acetyl-CoA in the peroxisome. Therefore, L-carnitine is important for the acetyl shuttle mechanism, transferring long-chain fatty acids between peroxisomes and mitochondria for subsequent β-oxidation during yeast growth on non-fermentable carbon sources such as fatty acids, acetate, and ethanol [4,7]. During yeast growth on these carbon sources, acetyl units are only produced in the cytosol and need to be transferred to the mitochondrial TCA cycle and to the peroxisomal/cytosolic glyoxylate cycle [9].…”