Supplementation with polyalcohols and sequential mixotrophy dilution photoinduction strategy boost the accumulation of astaxanthin by Haematococcus pluvialis

Mixotrophic Growth of Astaxanthin-Rich Alga Haematococcus pluvialis using Refined Crude Glycerol as Carbon Substrate: Batch and Fed-Batch Cultivations

“…The growth comparison is illustrated in Figure 2A, which shows that, under our experimental specifications, the green alga H. pluvialis could grow effectively under photoautotrophic and mixotrophic conditions, but there was virtually no growth under all heterotrophic conditions. Our results were similar to previous studies [68,71], which reported enhanced mixotrophic growth in the presence of glycerol. For heterotrophic conditions, the apparent growth of microalga was observed when cultures were supplemented with acetate; however, there has been no previous investigation on the use of glycerol.…”

“…Nevertheless, the highest value of ATX content (3.5 ± 0.4 % wt) was achieved with culture formerly cultivated using 7 g L -1 of refined crude glycerol. This obtained value was very similar to a previous study [71] which reported glycerol as the most promising substrate among 14 carbon sources in promoting H. pluvialis ATX production, and in the same order as many mixotrophic cultivations [45,69,72,84,85]. In addition, it can also be seen from the Table 2 that, only in presence of 7 g L -1 refined crude glycerol, H. pluvialis displayed an upward trend in ATX production until the end of the experiment (Figure 5B).…”

“…For photoautotrophically-grown culture, the maximum biomass concentration, also observed on day 5, was 0.50 ± 0.01 g DCW L -1 , which is approximately 1.2 -1.4 times lower than that of mixotrophically-grown cultures. A similar value of factor was reported by Azizi et al [71]. These observations were commonly expected, since mixotrophicallygrown cultures could utilize refined crude glycerol that was present, in addition to CO 2 , in promoting biomass accumulation.…”

“…Our obtained rates are in the same order as those observed from mixotrophic cultivations using technical-grade glycerol with a purity of 75 -80 % [68], implying the practical utilization of refined crude glycerol produced in our laboratory. Nevertheless, these rates are around 50 % less than the rate reported [71] when chemical-grade glycerol was used.…”

“…The use of crude glycerol for culturing various strains of microalgae for the purpose of enhancing biomass and bioproduct production has been well-demonstrated [57][58][59][60][61]. For H. pluvialis, although the microalga has been previously reported to grow using a number of organic carbon substrates [38,[62][63][64][65][66][67][68][69][70], there have only been a few studies on microalgal cultivation using glycerol [68,71]. Therefore, current limited knowledge of the use of biodiesel-derived glycerol for cultivating the green alga H. pluvialis has led to the conduction of this study, which aims to: 1) investigate the possibility of using biodiesel-derived glycerol as an organic carbon source, facilitating the growth of H. pluvialis batch culture under heterotrophic and mixotrophic conditions (the autotrophic growth condition was used as the control condition); 2) examine ATX accumulation in H. pluvialis cells, produced from different greenstage growth conditions, and 3) to investigate the use of repeated fed-batch cultivation as a tool to enhance the growth and ATX production of H. pluvialis.…”