Catalytic condition optimization in the conversion of nootkatone from valencene byYarrowia lipolytica

Abstract

Yarrowia lipolytica was a widespread and promising object in biotechnology, which was used to increase the biotransformation of valencene into nootkatone in shake flasks in this study. The main objective of this work is to determine the optimum combination of transformation conditions in shake flasks on the basis of single factor process optimization experiment. The results showed that Y. lipolytica was cultured in medium for 36 hr (exponential phase) and the amount of added Y. lipolytica was 5% (v/v). The concentration of substrate valencene was 920 mg·L−1, and the transformation time was 36 hr after adding substrates. Dimethyl sulfoxide, a water‐soluble organic solvent, was used as a co‐solvent with a concentration of 0.8% (v/v). The maximum production of nootkatone was 628.41 ± 18.60 mg·L−1 and the conversion rate was 68.30 ± 2.02% at cultivation conditions of 32°C, 150 rpm, and PH 5.30. The results showed that optimizing the catalytic conditions can significantly increase the yield of nootkatone by Y. lipolytica. Practical applications Recently, natural nootkatone is increasingly important due to its flavoring and physiological effects, but the amount of nootkatone in plants is low and cannot meet the demand. Also, there were few studies about microbial transformation of valencene by Yarrowia lipolytica under certain catalytic conditions. We demonstrated that optimizing the catalytic conditions can significantly increase the yield of nootkatone. Therefore, it provides a basis for the subsequent use of genetic engineering to transform Y. lipolytica to produce nootkatone.

Isolation, purification, and mass spectrometry identification of the enzyme involved in citrus flavor (+)‐valencene biotransformation to (+)‐nootkatone by Yarrowia lipolytica

“…The addition of Fe 2+ had the strongest promoting effect on the enzyme, and the enzyme activity was 4.42 times higher than that of the control group ( P < 0.001). In addition, it was found that the amount of (+)‐nootkatone was significantly increased when iron(II) sulfate was added to the initial medium 22 . This result indicated that the activity of ALDH reached the highest when pH was 6, and many metal ions can promote the activity of ALDH, especially Fe 2+ .…”

“…Spore suspension was prepared with 1–2 weeks of Y. lipolytica slope cultures and the concentration of spore suspension was adjusted to 10 6 –10 7 spores/mL. About 1 mL of spore suspension was cultivated in 50 mL yeast extract peptone dextrose media at 32 °C and 150 rpm for 36 h 22 . Y. lipolytica were harvested by centrifuging at 10 000 × g for 20 min.…”

Screening a Strain of Klebsiella sp. O852 and the Optimization of Fermentation Conditions for Trans-Dihydrocarvone Production

“…Besides, the production of other by-products may also lead to the decrease in the trans -dihydrocarvone yield. In the study of Li et al (2020), by-products were generated with the increase in biotransformation time, resulting in a decline in product yield [ 24 ]. Furthermore, with the increase in biotransformation time, the microorganism gradually entered the stationary phase and the decline phase, leading to a decrease in the catalytic capacity.…”

“…Hence, the optimum cultivation time was 4 h. The longer cultivation time could lead to cells hypoxia, which reduced the trans -dihydrocarvone yield [ 36 ]. Li et al (2020) found that the yield of the product reached the highest level when the substrate was added in the logarithmic growth phase [ 24 ]. Similar results were also reported by Gloria et al (2011) [ 37 ]…”

Advances on (+)-nootkatone microbial biosynthesis and its related enzymes

“…Moreover, they designed the three-phase partitioning bioreactor and four-phase partitioning bioreactor to produce (+)-nootkatone from (+)-valencene by Y. lipolytica 2.2ab (Castillo-Araiza et al, 2017 ; Palmerín-Carreño et al, 2016 ). In addition, Li et al optimized the catalytic conditions of the biotransformation of (+)-valencene into (+)-nootkatone by Y. lipolytica in shake flasks and the maximum production of (+)-nootkatone reached 628.41 ± 18.60 mg/l (Li et al, 2021 ).…”