Evaluation of the Potential of Lipid-Extracted Chlorella vulgaris Residue for Yarrowia lipolytica Growth at Different pH Levels.

Projections show that the cultivation of microalgae will extend to the production of bio-based compounds, such as biofuels, cosmetics, and medicines. This will generate co-products or residues that will need to be valorized to reduce the environmental impact and the cost of the process. This study explored the ability of lipid-extracted Chlorella vulgaris residue as a sole carbon and nitrogen source for growing oleaginous yeasts without any pretreatment. Both wild-type Yarrowia lipolytica W29 and mutant JMY3501 (which was designed to accumulate more lipids without their remobilization or degradation) showed a similar growth rate of 0.28 h-1 at different pH levels (3.5, 5.5, and 7.5). However, the W29 cell growth had the best cell number on microalgal residue at a pH of 7.5, while three times fewer cells were produced at all pH levels when JMY3501 was grown on microalgal residue. The JMY3501 growth curves were similar at pH 3.5, 5.5, and 7.5, while the fatty-acid composition differed significantly, with an accumulation of α-linolenic acid on microalgal residue at a pH of 7.5. Our results demonstrate the potential valorization of Chlorella vulgaris residue for Yarrowia lipolytica growth and the positive effect of a pH of 7.5 on the fatty acid profile.

Improvement of protein content and decrease of anti-nutritional factors in olive cake by solid-state fermentation: A way to valorize this industrial by-product in animal feed.

The present work investigates the bioconversion of the olive cake (OC) generated by olive oil industries in Morocco through solid-state fermentation using selected filamentous fungi to increase its nutritional values for subsequent valorization as ruminants feed. The fungi, namely Beauveria bassiana, Fusarium flocciferum, Rhizodiscina cf. lignyota, and Aspergillus niger were cultured on OC for 15 days. Chemical composition as well as enzymes activities were determined. Results showed (i) an increase in protein content of up to 94% for treated OC and (ii) significant (P < 0.05) decreases of phenolic compounds, up to 43%, 70% and 42% for total phenolic content, total flavonoids content, and total condensed tannins, respectively. Moreover, the RP-HPLC analysis of fermented OC confirmed the degradation of individual phenolic compounds by the strains. These findings demonstrate that F. flocciferum and Rhizodiscina cf. lignyota are efficient enzymes producers leading to a nutritive enhancement of this by-product.