Limits...
Conversion of biomass-derived oligosaccharides into lipids.

Gong Z, Wang Q, Shen H, Wang L, Xie H, Zhao ZK - Biotechnol Biofuels (2014)

Bottom Line: Biomass hydrolysates usually contain monosaccharides as well as various amounts of oligosaccharides.C. curvatus can directly utilize biomass-derived oligosaccharides.Oligocelluloses are transported into the cells and then hydrolyzed by cytoplasmic enzymes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dalian National Laboratory for Clean Energy and Dalian Institute of Chemical Physics, CAS, 457 Zhongshan Road, Dalian 116023, PR China. zhaozb@dicp.ac.cn.

ABSTRACT

Background: Oligocelluloses and oligoxyloses are partially hydrolyzed products from lignocellulosic biomass hydrolysis. Biomass hydrolysates usually contain monosaccharides as well as various amounts of oligosaccharides. To utilize biomass hydrolysates more efficiently, it is important to identify microorganisms capable of converting biomass-derived oligosaccharides into biofuels or biochemicals.

Results: We have demonstrated that the oleaginous yeast Cryptococcus curvatus can utilize either oligocelluloses or oligoxyloses as sole carbon sources for microbial lipid production. When oligocelluloses were used, lipid content and lipid coefficient were 35.9% and 0.20 g/g consumed sugar, respectively. When oligoxyloses were used, lipid coefficient was 0.17 g/g consumed sugar. Ion chromatography analysis showed oligocelluloses with a degree of polymerization from 2 to 9 were assimilated. Our data suggested that these oligosaccharides were transported into cells and then hydrolyzed by cytoplasmic enzymes. Further analysis indicated that these enzymes were inducible by oligocelluloses. Lipid production on cellulose by C. curvatus using the simultaneous saccharification and lipid production process in the absence of cellobiase achieved essentially identical results to that in the presence of cellobiase, suggesting that oligocelluloses generated in situ were utilized with high efficiency. This study has provided inspiring information for oligosaccharides utilization, which should facilitate biorefinery based on lignocellulosic biomass.

Conclusions: C. curvatus can directly utilize biomass-derived oligosaccharides. Oligocelluloses are transported into the cells and then hydrolyzed by cytoplasmic enzymes. A simultaneous saccharification and lipid production process can be conducted without oligocelluloses accumulation in the absence of cellobiase by C. curvatus, which could reduce the enzyme costs.

No MeSH data available.


Related in: MedlinePlus

Time course of glucose and cellobiose evolution during biochemical conversion of cellulose. (A) Enzymatic hydrolysis by cellulase in the presence of cellobiase. (B) Enzymatic hydrolysis by cellulase in the presence of heat-inactivated cellobiase. (C) Conversion by C. curvatus cells according to the SSLP process with heat-inactivated cellobiase. Initial cellulose concentration was 40 g/L. Cellulase and cellobiase were loaded at 15 FPU and 30 CBU per gram of cellulose. Hydrolysis was done at 50°C, 200 rpm in 0.05 M citrate buffer (pH 4.8). C. curvatus cells were cultured at 30°C, 200 rpm. CBU, cellobiase unit; FPU, filter paper unit; SSLP, simultaneous saccharification and lipid production.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC3927853&req=5

Figure 7: Time course of glucose and cellobiose evolution during biochemical conversion of cellulose. (A) Enzymatic hydrolysis by cellulase in the presence of cellobiase. (B) Enzymatic hydrolysis by cellulase in the presence of heat-inactivated cellobiase. (C) Conversion by C. curvatus cells according to the SSLP process with heat-inactivated cellobiase. Initial cellulose concentration was 40 g/L. Cellulase and cellobiase were loaded at 15 FPU and 30 CBU per gram of cellulose. Hydrolysis was done at 50°C, 200 rpm in 0.05 M citrate buffer (pH 4.8). C. curvatus cells were cultured at 30°C, 200 rpm. CBU, cellobiase unit; FPU, filter paper unit; SSLP, simultaneous saccharification and lipid production.

Mentions: To further demonstrate the benefit that C. curvatus could offer in biochemical conversion of cellulose, we monitored the evolution of glucose and cellobiose under different conditions (Figure 7). When cellulose was treated with cellulase in the presence of an appropriate amount of Aspergillus niger cellobiase, cellobiose was barely accumulated (Figure 7A). However, when cellobiase was heat-inactivated, cellobiose reached 7.0 g/L during the first 12 h, and then gradually dropped to 4.2 g/L at 72 h. Moreover, glucose was produced with a substantial lower rate in the early stage (Figure 7B). These results clearly indicate that the presence of active cellobiase is crucial for efficient hydrolysis of cellulose. Interestingly, cellobiose concentration was always below 0.7 g/L during the SSLP process supplemented with heat-inactivated cellobiase (Figure 7C), suggesting that C. curvatus cells produced sufficient hydrolytic enzymes to remove cellobiose. More importantly, there was no oligocellulose accumulation during the SSLP process (data not shown). In sharp contrast, a previous study using a simultaneous saccharification and fermentation process in the presence of cellulase with low cellobiase activity reported that cellobiose reached 10.3 g/L within 72 h when 80 g/L of alkaline-pretreated corn stover was used for ethanol production by S. cerevisiae[7]. Thus, in that case, additional cellobiase was used to remove cellobiose and improve ethanol yield. Taken together, C. curvatus showed exceptional capacity to metabolize oligosaccharides, which enabled direct yet efficient utilization of cellulose for lipid production in the presence of cellulase only.


Conversion of biomass-derived oligosaccharides into lipids.

Gong Z, Wang Q, Shen H, Wang L, Xie H, Zhao ZK - Biotechnol Biofuels (2014)

Time course of glucose and cellobiose evolution during biochemical conversion of cellulose. (A) Enzymatic hydrolysis by cellulase in the presence of cellobiase. (B) Enzymatic hydrolysis by cellulase in the presence of heat-inactivated cellobiase. (C) Conversion by C. curvatus cells according to the SSLP process with heat-inactivated cellobiase. Initial cellulose concentration was 40 g/L. Cellulase and cellobiase were loaded at 15 FPU and 30 CBU per gram of cellulose. Hydrolysis was done at 50°C, 200 rpm in 0.05 M citrate buffer (pH 4.8). C. curvatus cells were cultured at 30°C, 200 rpm. CBU, cellobiase unit; FPU, filter paper unit; SSLP, simultaneous saccharification and lipid production.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3927853&req=5

Figure 7: Time course of glucose and cellobiose evolution during biochemical conversion of cellulose. (A) Enzymatic hydrolysis by cellulase in the presence of cellobiase. (B) Enzymatic hydrolysis by cellulase in the presence of heat-inactivated cellobiase. (C) Conversion by C. curvatus cells according to the SSLP process with heat-inactivated cellobiase. Initial cellulose concentration was 40 g/L. Cellulase and cellobiase were loaded at 15 FPU and 30 CBU per gram of cellulose. Hydrolysis was done at 50°C, 200 rpm in 0.05 M citrate buffer (pH 4.8). C. curvatus cells were cultured at 30°C, 200 rpm. CBU, cellobiase unit; FPU, filter paper unit; SSLP, simultaneous saccharification and lipid production.
Mentions: To further demonstrate the benefit that C. curvatus could offer in biochemical conversion of cellulose, we monitored the evolution of glucose and cellobiose under different conditions (Figure 7). When cellulose was treated with cellulase in the presence of an appropriate amount of Aspergillus niger cellobiase, cellobiose was barely accumulated (Figure 7A). However, when cellobiase was heat-inactivated, cellobiose reached 7.0 g/L during the first 12 h, and then gradually dropped to 4.2 g/L at 72 h. Moreover, glucose was produced with a substantial lower rate in the early stage (Figure 7B). These results clearly indicate that the presence of active cellobiase is crucial for efficient hydrolysis of cellulose. Interestingly, cellobiose concentration was always below 0.7 g/L during the SSLP process supplemented with heat-inactivated cellobiase (Figure 7C), suggesting that C. curvatus cells produced sufficient hydrolytic enzymes to remove cellobiose. More importantly, there was no oligocellulose accumulation during the SSLP process (data not shown). In sharp contrast, a previous study using a simultaneous saccharification and fermentation process in the presence of cellulase with low cellobiase activity reported that cellobiose reached 10.3 g/L within 72 h when 80 g/L of alkaline-pretreated corn stover was used for ethanol production by S. cerevisiae[7]. Thus, in that case, additional cellobiase was used to remove cellobiose and improve ethanol yield. Taken together, C. curvatus showed exceptional capacity to metabolize oligosaccharides, which enabled direct yet efficient utilization of cellulose for lipid production in the presence of cellulase only.

Bottom Line: Biomass hydrolysates usually contain monosaccharides as well as various amounts of oligosaccharides.C. curvatus can directly utilize biomass-derived oligosaccharides.Oligocelluloses are transported into the cells and then hydrolyzed by cytoplasmic enzymes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dalian National Laboratory for Clean Energy and Dalian Institute of Chemical Physics, CAS, 457 Zhongshan Road, Dalian 116023, PR China. zhaozb@dicp.ac.cn.

ABSTRACT

Background: Oligocelluloses and oligoxyloses are partially hydrolyzed products from lignocellulosic biomass hydrolysis. Biomass hydrolysates usually contain monosaccharides as well as various amounts of oligosaccharides. To utilize biomass hydrolysates more efficiently, it is important to identify microorganisms capable of converting biomass-derived oligosaccharides into biofuels or biochemicals.

Results: We have demonstrated that the oleaginous yeast Cryptococcus curvatus can utilize either oligocelluloses or oligoxyloses as sole carbon sources for microbial lipid production. When oligocelluloses were used, lipid content and lipid coefficient were 35.9% and 0.20 g/g consumed sugar, respectively. When oligoxyloses were used, lipid coefficient was 0.17 g/g consumed sugar. Ion chromatography analysis showed oligocelluloses with a degree of polymerization from 2 to 9 were assimilated. Our data suggested that these oligosaccharides were transported into cells and then hydrolyzed by cytoplasmic enzymes. Further analysis indicated that these enzymes were inducible by oligocelluloses. Lipid production on cellulose by C. curvatus using the simultaneous saccharification and lipid production process in the absence of cellobiase achieved essentially identical results to that in the presence of cellobiase, suggesting that oligocelluloses generated in situ were utilized with high efficiency. This study has provided inspiring information for oligosaccharides utilization, which should facilitate biorefinery based on lignocellulosic biomass.

Conclusions: C. curvatus can directly utilize biomass-derived oligosaccharides. Oligocelluloses are transported into the cells and then hydrolyzed by cytoplasmic enzymes. A simultaneous saccharification and lipid production process can be conducted without oligocelluloses accumulation in the absence of cellobiase by C. curvatus, which could reduce the enzyme costs.

No MeSH data available.


Related in: MedlinePlus