Limits...
Evaluating the effects of biocompatible cholinium ionic liquids on microbial lipid production by Trichosporon fermentans.

Liu L, Hu Y, Wen P, Li N, Zong M, Ou-Yang B, Wu H - Biotechnol Biofuels (2015)

Bottom Line: Despite the reduction in lipid content, the lipid production by T. fermentans was improved in the presence of low concentrations of [Ch][Lys] (≤30 mM) and [Ch][Ser] (≤20 mM) due to the remarkable increase of biomass.However, the anions of [Ch][Lys] and [Ch][Ser] could be assimilated as nitrogen source by T. fermentans and the reduced C/N ratio accounts for the inhibition of lipid accumulation, which could be alleviated by improving C/N ratio of medium.The anions of [Ch][Lys], [Ch][Ser] and [Ch][OAc] play an important role in affecting the cell growth and lipid accumulation of T. fermentans, and the inhibition of these three ILs on lipid production can be alleviated by careful fermentation condition control.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences and Bioengineering, Guangzhou Higher Education Mega Centre, South China University of Technology, 382 East Waihuan Rd., Panyu District, Guangzhou, 510640 China.

ABSTRACT

Background: Microbial lipid is a potential raw material for large-scale biodiesel production and lignocellulosic hydrolysate has been considered as promising low-cost substrate for lipid fermentation. Lignocellulosic biomass needs to be pretreated before enzymatic hydrolysis, and biocompatible cholinium ionic liquids (ILs) have been demonstrated to be highly efficient for pretreatment. However, the impact of these ILs residues in hydrolysates on downstream biotransformation remains unknown. Therefore, the influence of three typical cholinium ILs on the lipid production by Trichosporon fermentans was first investigated.

Results: The cell growth of T. fermentans was stimulated in the presence of cholinium lysine ([Ch][Lys]) and cholinium serine ([Ch][Ser]), while the lipid accumulation was inhibited by [Ch][Lys]) and [Ch][Ser]. Both cell growth and lipid accumulation of T. fermentans were inhibited in the presence of cholinium acetate ([Ch][OAc]). Despite the reduction in lipid content, the lipid production by T. fermentans was improved in the presence of low concentrations of [Ch][Lys] (≤30 mM) and [Ch][Ser] (≤20 mM) due to the remarkable increase of biomass. It was found that cholinium cation had minor influence on lipid production. However, the anions of [Ch][Lys] and [Ch][Ser] could be assimilated as nitrogen source by T. fermentans and the reduced C/N ratio accounts for the inhibition of lipid accumulation, which could be alleviated by improving C/N ratio of medium. In addition, the anion of [Ch][OAc] could be metabolized by T. fermentans, leading to a rapid alkaline-pH shift and strong inhibition of lipid production. And this inhibitory effect on lipid production could be significantly reduced by controlling culture pH.

Conclusions: The anions of [Ch][Lys], [Ch][Ser] and [Ch][OAc] play an important role in affecting the cell growth and lipid accumulation of T. fermentans, and the inhibition of these three ILs on lipid production can be alleviated by careful fermentation condition control. Hence, T. fermentans is a promising strain for microbial lipid production from cholinium ILs-pretreated lignocellulosic hydrolysates.

No MeSH data available.


Related in: MedlinePlus

Effect of medium pH on the lipid production by T. fermentans in the presence of [Ch][OAc]. a pH profile of T. fermentans in the presence of [Ch][OAc]. b Cell growth and lipid accumulation of T. fermentans in the presence of [Ch][OAc] with pH control. The results are mean of two experiments, and error bars represent standard deviations from mean value.
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Fig5: Effect of medium pH on the lipid production by T. fermentans in the presence of [Ch][OAc]. a pH profile of T. fermentans in the presence of [Ch][OAc]. b Cell growth and lipid accumulation of T. fermentans in the presence of [Ch][OAc] with pH control. The results are mean of two experiments, and error bars represent standard deviations from mean value.

Mentions: It was reported that the inhibition effect of [Emim][OAc] on lipid production by R. toruloides was mainly due to a rapid alkaline-pH shift resulted from the assimilation of [OAc]− [13]. In this study, the [OAc]− of [Ch][OAc] was also metabolized by T. fermentans. Hence, the evolution of culture pH in the presence or absence of [Ch][OAc] was detected during fermentation. As can be seen in Fig. 5a, the culture pH shifted from 6.5 to 7.3 within 24 h and then tardily increased to 7.5 in the presence of 30 mM [Ch][OAc], while it dropped from 6.5 to 4.8 for the control. To investigate whether the pH change was the major reason for the inhibitory effect of [Ch][OAc] on lipid production by T. fermentans, cells were cultured under the controlled pH conditions in the presence of 30 mM [Ch][OAc]. Meanwhile, the control experiments were performed at the same conditions without IL. As shown in Fig. 5b, when cultures were maintained at pH 5.0, the values of biomass, lipid content, and lipid yield obtained in the presence of 30 mM [Ch][OAc] were the maximal, which were also very close to those achieved in the absence of [Ch][OAc]. For shake-flask fermentation of T. fermentans without pH control, the maximal values of biomass, lipid content, and lipid yield were found to be obtained at initial pH of 6.5 [27], which can be explained from the variation of culture pH as indicated in Fig. 5a (at approximately 5.0 during most of the time). The biomass, lipid content, and lipid yield decreased with the increase of controlled pH from 5.0 to 7.5, and the reduction in biomass and lipid yield was significant (p < 0.05) while it was insignificant for lipid content (p > 0.05). Therefore, the alkaline-pH change through assimilation of [OAc]− accounts for the inhibitory effect of [Ch][OAc] on lipid production by T. fermentans.Fig. 5


Evaluating the effects of biocompatible cholinium ionic liquids on microbial lipid production by Trichosporon fermentans.

Liu L, Hu Y, Wen P, Li N, Zong M, Ou-Yang B, Wu H - Biotechnol Biofuels (2015)

Effect of medium pH on the lipid production by T. fermentans in the presence of [Ch][OAc]. a pH profile of T. fermentans in the presence of [Ch][OAc]. b Cell growth and lipid accumulation of T. fermentans in the presence of [Ch][OAc] with pH control. The results are mean of two experiments, and error bars represent standard deviations from mean value.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4536777&req=5

Fig5: Effect of medium pH on the lipid production by T. fermentans in the presence of [Ch][OAc]. a pH profile of T. fermentans in the presence of [Ch][OAc]. b Cell growth and lipid accumulation of T. fermentans in the presence of [Ch][OAc] with pH control. The results are mean of two experiments, and error bars represent standard deviations from mean value.
Mentions: It was reported that the inhibition effect of [Emim][OAc] on lipid production by R. toruloides was mainly due to a rapid alkaline-pH shift resulted from the assimilation of [OAc]− [13]. In this study, the [OAc]− of [Ch][OAc] was also metabolized by T. fermentans. Hence, the evolution of culture pH in the presence or absence of [Ch][OAc] was detected during fermentation. As can be seen in Fig. 5a, the culture pH shifted from 6.5 to 7.3 within 24 h and then tardily increased to 7.5 in the presence of 30 mM [Ch][OAc], while it dropped from 6.5 to 4.8 for the control. To investigate whether the pH change was the major reason for the inhibitory effect of [Ch][OAc] on lipid production by T. fermentans, cells were cultured under the controlled pH conditions in the presence of 30 mM [Ch][OAc]. Meanwhile, the control experiments were performed at the same conditions without IL. As shown in Fig. 5b, when cultures were maintained at pH 5.0, the values of biomass, lipid content, and lipid yield obtained in the presence of 30 mM [Ch][OAc] were the maximal, which were also very close to those achieved in the absence of [Ch][OAc]. For shake-flask fermentation of T. fermentans without pH control, the maximal values of biomass, lipid content, and lipid yield were found to be obtained at initial pH of 6.5 [27], which can be explained from the variation of culture pH as indicated in Fig. 5a (at approximately 5.0 during most of the time). The biomass, lipid content, and lipid yield decreased with the increase of controlled pH from 5.0 to 7.5, and the reduction in biomass and lipid yield was significant (p < 0.05) while it was insignificant for lipid content (p > 0.05). Therefore, the alkaline-pH change through assimilation of [OAc]− accounts for the inhibitory effect of [Ch][OAc] on lipid production by T. fermentans.Fig. 5

Bottom Line: Despite the reduction in lipid content, the lipid production by T. fermentans was improved in the presence of low concentrations of [Ch][Lys] (≤30 mM) and [Ch][Ser] (≤20 mM) due to the remarkable increase of biomass.However, the anions of [Ch][Lys] and [Ch][Ser] could be assimilated as nitrogen source by T. fermentans and the reduced C/N ratio accounts for the inhibition of lipid accumulation, which could be alleviated by improving C/N ratio of medium.The anions of [Ch][Lys], [Ch][Ser] and [Ch][OAc] play an important role in affecting the cell growth and lipid accumulation of T. fermentans, and the inhibition of these three ILs on lipid production can be alleviated by careful fermentation condition control.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences and Bioengineering, Guangzhou Higher Education Mega Centre, South China University of Technology, 382 East Waihuan Rd., Panyu District, Guangzhou, 510640 China.

ABSTRACT

Background: Microbial lipid is a potential raw material for large-scale biodiesel production and lignocellulosic hydrolysate has been considered as promising low-cost substrate for lipid fermentation. Lignocellulosic biomass needs to be pretreated before enzymatic hydrolysis, and biocompatible cholinium ionic liquids (ILs) have been demonstrated to be highly efficient for pretreatment. However, the impact of these ILs residues in hydrolysates on downstream biotransformation remains unknown. Therefore, the influence of three typical cholinium ILs on the lipid production by Trichosporon fermentans was first investigated.

Results: The cell growth of T. fermentans was stimulated in the presence of cholinium lysine ([Ch][Lys]) and cholinium serine ([Ch][Ser]), while the lipid accumulation was inhibited by [Ch][Lys]) and [Ch][Ser]. Both cell growth and lipid accumulation of T. fermentans were inhibited in the presence of cholinium acetate ([Ch][OAc]). Despite the reduction in lipid content, the lipid production by T. fermentans was improved in the presence of low concentrations of [Ch][Lys] (≤30 mM) and [Ch][Ser] (≤20 mM) due to the remarkable increase of biomass. It was found that cholinium cation had minor influence on lipid production. However, the anions of [Ch][Lys] and [Ch][Ser] could be assimilated as nitrogen source by T. fermentans and the reduced C/N ratio accounts for the inhibition of lipid accumulation, which could be alleviated by improving C/N ratio of medium. In addition, the anion of [Ch][OAc] could be metabolized by T. fermentans, leading to a rapid alkaline-pH shift and strong inhibition of lipid production. And this inhibitory effect on lipid production could be significantly reduced by controlling culture pH.

Conclusions: The anions of [Ch][Lys], [Ch][Ser] and [Ch][OAc] play an important role in affecting the cell growth and lipid accumulation of T. fermentans, and the inhibition of these three ILs on lipid production can be alleviated by careful fermentation condition control. Hence, T. fermentans is a promising strain for microbial lipid production from cholinium ILs-pretreated lignocellulosic hydrolysates.

No MeSH data available.


Related in: MedlinePlus