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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 the selected cholinium ILs on sugar metabolism and lipid coefficient of T. fermentans.a Glucose consumption, b xylose consumption, and c lipid coefficient of T. fermentans in the presence of the cholinium ILs. The results are mean of two experiments, and error bars represent standard deviations from mean value.
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Fig3: Effect of the selected cholinium ILs on sugar metabolism and lipid coefficient of T. fermentans.a Glucose consumption, b xylose consumption, and c lipid coefficient of T. fermentans in the presence of the cholinium ILs. The results are mean of two experiments, and error bars represent standard deviations from mean value.

Mentions: To better understand the effect of the tested cholinium ILs on the cell growth and lipid accumulation of T. fermentans, the concentrations of residual sugars in the fermentation media after 4 days’ cultivation were measured. As shown in Fig. 3a, b, the residual glucose and xylose in the fermentation medium without ILs were 9.4 and 16.0 g/L, respectively. More glucose and xylose were consumed by T. fermentans in the presence of [Ch][Lys] and [Ch][Ser]. Specifically, the stimulation effect of [Ch][Lys] on sugar utilization was stronger than that of [Ch][Ser]. It was worth noting that when [Ch][Lys] was present at 30 mM, the glucose and xylose were almost exhausted by T. fermentans, which well explained the highest biomass achieved at this point. However, greater [Ch][Lys] in the media (above 30 mM) resulted in a slight drop in glucose consumption but a sharp decline in xylose consumption. Similar phenomenon was also observed in the presence of [Ch][Ser]. Interestingly, in the presence of [Ch][Lys] and [Ch][Ser], the extra sugar consumed by T. fermentans were not transformed into lipid indicated by the lower lipid coefficient in most cases compared with the control (Fig. 3c). In contrast, except that at its low concentration (≤10 mM), [Ch][OAc] showed inhibitory effect on both glucose and xylose metabolism of T. fermentans, and the inhibition increased with the increase of which concentration. Albeit more glucose and xylose were consumed when the concentration of [Ch][OAc] was below 10 mM, there was no improvement in the biomass and lipid content of T. fermentans, suggesting that the extra sugar consumed was not used for cell growth and lipid synthesis. Similar phenomenon was also observed in studying the influence of organic acids on T. fermentans’ lipid production [23]. It was reported that acetic acid (acetate) could interfere with yeast metabolism, which increased in the ATP requirement for cell maintenance [24, 25]. Hence, it is possible that the extra consumed sugars were used for synthesis of ATP. However, the actual mechanism still needs further investigation.Fig. 3


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 the selected cholinium ILs on sugar metabolism and lipid coefficient of T. fermentans.a Glucose consumption, b xylose consumption, and c lipid coefficient of T. fermentans in the presence of the cholinium ILs. 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

Fig3: Effect of the selected cholinium ILs on sugar metabolism and lipid coefficient of T. fermentans.a Glucose consumption, b xylose consumption, and c lipid coefficient of T. fermentans in the presence of the cholinium ILs. The results are mean of two experiments, and error bars represent standard deviations from mean value.
Mentions: To better understand the effect of the tested cholinium ILs on the cell growth and lipid accumulation of T. fermentans, the concentrations of residual sugars in the fermentation media after 4 days’ cultivation were measured. As shown in Fig. 3a, b, the residual glucose and xylose in the fermentation medium without ILs were 9.4 and 16.0 g/L, respectively. More glucose and xylose were consumed by T. fermentans in the presence of [Ch][Lys] and [Ch][Ser]. Specifically, the stimulation effect of [Ch][Lys] on sugar utilization was stronger than that of [Ch][Ser]. It was worth noting that when [Ch][Lys] was present at 30 mM, the glucose and xylose were almost exhausted by T. fermentans, which well explained the highest biomass achieved at this point. However, greater [Ch][Lys] in the media (above 30 mM) resulted in a slight drop in glucose consumption but a sharp decline in xylose consumption. Similar phenomenon was also observed in the presence of [Ch][Ser]. Interestingly, in the presence of [Ch][Lys] and [Ch][Ser], the extra sugar consumed by T. fermentans were not transformed into lipid indicated by the lower lipid coefficient in most cases compared with the control (Fig. 3c). In contrast, except that at its low concentration (≤10 mM), [Ch][OAc] showed inhibitory effect on both glucose and xylose metabolism of T. fermentans, and the inhibition increased with the increase of which concentration. Albeit more glucose and xylose were consumed when the concentration of [Ch][OAc] was below 10 mM, there was no improvement in the biomass and lipid content of T. fermentans, suggesting that the extra sugar consumed was not used for cell growth and lipid synthesis. Similar phenomenon was also observed in studying the influence of organic acids on T. fermentans’ lipid production [23]. It was reported that acetic acid (acetate) could interfere with yeast metabolism, which increased in the ATP requirement for cell maintenance [24, 25]. Hence, it is possible that the extra consumed sugars were used for synthesis of ATP. However, the actual mechanism still needs further investigation.Fig. 3

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