Evaluating The Potential Of Phytohormones Supplementation For Biomass And Fatty Acids Enhancement In Thraustochytrid Strains

In recent years,thraustochytrids have received worldwide attention as a sustainable and renewable source of fatty acids(FAs)production.However,the low productivity of fatty acids in thraustochytrids restrained its industrial application.Various approaches have been carried out to improve the FAs yield.Phytohormones,which participate in the manipulation of multiple physiological processes,were proved to increase FAs accumulation in microalgae.Yet,the influence of phytohormones supplementation as a fermentation strategy on thraustochytrids culture is poorly investigated.The present study was undertaken to evaluate the potential effect of five selected phytohormones,namely,gibberellic acid(GA),indole-3-acetic acid(IAA),kinetin(Kin),abscisic acid(ABS),and salicylic acid(SA)on biomass and fatty acids accumulation in two thraustochytrids strains specifically,Schizochytrium sp.PKU#Mn4 and Thraustochytriidae sp.PKU#Sw8 under standard and nitrogen-limited conditions.At 0h supplementation,kinetin(5 mg/L)and indole acetic acid(1mg/L)enhanced biomass by 31 %,23% for PKU#Mn4.Yet,an increment of 32% and 30% in comparison to the control group was observed for fatty acid production.The effect of indole acetic acid(1 mg/L)was more pronounced as compared to the other phytohormones on biomass,and fatty acids production of PKU#Sw8,with respectively 1.07-fold and1.34-fold increase.The effect of phytohormones supplementation was also shown to be time-dependent.The feeding of IAA(1 mg/L)at 48 h to PKU#Mn4 and Kin(0.1 mg/L)at 24 h to PKU#Sw8 led to even higher biomass and fatty acids production.In fact,the increase on biomass and fatty acids production for IAA and Kin are respectively 20% and 33% for PKU#Mn4,51% and 34% for PKU#Sw8 in comparison to 0h test resultsTo further increase the biomass and FAs production,the effect of phytohormones supplementation under nitrogen-optimized conditions was evaluated,here yeast extract(Y.extract)(0.5-1g/L)and peptone(pep)(0.5-1.5g/L)were analyzed for both strains,the result showed that a combination of Kin(4 mg/L)and Y.extract(1 g/L)increased biomass and fatty acids production in PKU#Mn4 strain,i.e.,31% and 30%respectively,in comparison to optimized M4 medium without phytohormones.Meanwhile,for PKU#Sw8 strain,the combination of yeast extract,peptone,and Kin(5 mg/L)increased the biomass and fatty acids production by 29% and 27%,respectively.The current study presents phytohormones supplementation as a promising strategy for the enhancement of biomass and FAs production in thraustochytrids.