Astaxanthin preparation by fermentation of esters from Haematococcus pluvialis algal extracts with Stenotrophomonas species

Abstract

Natural astaxanthin (Ax) is an additive that is widely used because of its beneficial biochemical functions. However, the methods used to produce free Ax have drawbacks. Chemical saponification methods produce several by-products, and lipase-catalyzed hydrolysis methods are not cost effective. In this study, a bacterial strain of Stenotrophomonas sp. was selected to enzymatically catalyze the saponification of Ax esters to produce free all-trans-Ax. Through single-factor experiments and a Box-Behnken design, the optimal fermentation conditions were determined as follows: a seed culture age of 37.79 h, an inoculum concentration of 5.92%, and an initial broth pH of 6.80. Under these conditions, a fermentation curve was drawn, and the optimal fermentation time was shown to be 60 h. At 60 h, the degradation rate of the Ax esters was 98.08%, and the yield of free all-trans-Ax was 50.130 μg/mL. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:649-656, 2016.

Highly efficient preparation of free all‐trans‐astaxanthin from Haematococcus pluvialis extract by a rapid biocatalytic method based on crude extracellular enzyme extract

“…Since Dong et al . () already proved the preparation of free astaxanthin by a fermentation process with S. maltophilia , herein the crude extracellular enzyme extract of P. aeruginosa was applied to catalyse the hydrolysis of astaxanthin esters. This strain was grown in flask, and the supernatant of the fermentation broth was used to check the presence of extracellular hydrolytic enzymes.…”

“…() and Dong et al . (), which extracted the reaction with isopropanol/dichloromethane (1/1, v/v) mixture and with dichloromethane, respectively. In fact, these latter methods required a larger amount of total organic solvent.…”

“…). In fact, free astaxanthin is spontaneously converted into these side products in the presence of light, oxygen and heat (Dong et al ., ). It was worth to emphasise that the biocatalytic reaction required mild conditions and the one herein studied was quite rapid and no destabilising for all‐ trans ‐astaxanthin (few side products were noted in the HPLC analysis).…”

“…The injection volume was 20 μL. The ratio of hydrolysis of astaxanthin esters to free astaxanthin was calculated from the corresponding chromatographic peak area (Dong et al ., ) by the following formula:…”

“…Dong et al . () produced free astaxanthin by hydrolysis of H. pluvialis oil added to a fermentation of Stenotrophomonas sp. The hydrolytic ratio of astaxanthin esters after 60 h fermentation was 98.1%, and the production of astaxanthin was about 10 μg per mg of oil added.…”