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Production of poly(3-hydroxybutyrate) by Halomonas boliviensis in an air-lift reactor.

Rivera-Terceros P, Tito-Claros E, Torrico S, Carballo S, Van-Thuoc D, Quillaguamán J - J Biol Res (Thessalon) (2015)

Bottom Line: The largest amount of PHB, 41 % (wt.), was attained after 24 hrs of cultivation during which maltose in the hydrolysate was assimilated more rapidly than glucose during active cell growth; however, the rate of assimilation of both the carbohydrates was found to be similar during synthesis of PHB.Both maltose and glucose in the hydrolysate induce cell growth and PHB synthesis; most likely the cells balance adequately CoA and NAD(P)H during the assimilation of these carbohydrates.The combination of cheap substrates, simple production systems and the use of non-strict sterile conditions by the halophile H. boliviensis are desirable traits for large scale production of PHB, and should lead to a competitive bioprocess.

View Article: PubMed Central - PubMed

Affiliation: Center of Biotechnology, Faculty of Sciences and Technology, San Simon University, Cochabamba, Bolivia.

ABSTRACT

Background: Microbial polyesters, also known as polyhydroxyalkanoates (PHAs), closely resemble physical and mechanical features of petroleum derived plastics. Recombinant Escherichia coli strains are being used in industrial production of PHAs in Stirred Tank Bioreactors (STRs). However, use of Air-Lift Reactors (ALRs) has been known to offer numerous technical operating options over STRs, and as such has been successfully implemented in many bioprocesses. Halomonas boliviensis is a halophilic bacterium that is known to assimilate various carbohydrates and convert them into a particular type of PHA known as poly(3-hydroxybutyrate) (PHB). Owing to this capability, it has been used to synthesize the polyester using hydrolysates of starch or wheat bran in stirred tank bioreactors.

Results: This research article firstly describes the production of PHB in shake flasks by H. boliviensis using different combinations of carbohydrates and partially hydrolyzed starch as carbon sources. The highest PHB yields, between 56 and 61 % (wt.), were achieved when either starch hydrolysate or a mixture of glucose and xylose were used as carbon sources. The starch hydrolysate obtained in this study was then used as carbon source in an ALR. The largest amount of PHB, 41 % (wt.), was attained after 24 hrs of cultivation during which maltose in the hydrolysate was assimilated more rapidly than glucose during active cell growth; however, the rate of assimilation of both the carbohydrates was found to be similar during synthesis of PHB. An incomplete pentose phosphate pathway, which lacks 6-phosphogluconate dehydrogenase, was deduced from the genome sequence of this bacterium and may result in the characteristic assimilation of glucose and maltose by the cells.

Conclusions: This study showed that the production of PHB by H. boliviensis using cheap substrates such as starch hydrolysate in a simple production system involving an ALR is feasible. Both maltose and glucose in the hydrolysate induce cell growth and PHB synthesis; most likely the cells balance adequately CoA and NAD(P)H during the assimilation of these carbohydrates. The combination of cheap substrates, simple production systems and the use of non-strict sterile conditions by the halophile H. boliviensis are desirable traits for large scale production of PHB, and should lead to a competitive bioprocess.

No MeSH data available.


Related in: MedlinePlus

The Entner-Doudoroff and the pentose phosphate pathways in H. boliviensis. Enzymes highlighted in blue were the subject of this study. Numbers and abbreviations for each metabolic step refer to the number of alleles and the cluster that the alleles formed with: P, Proteobacteria; B, bacteria; T, thermophilic archaea; A, non-thermophilic archaea and combinations of these groups of organisms. Database accession numbers for enzymes of H. boliviensis are provided in Table 2. EC numbers for the enzymes in the metabolisms are pointed out as classified in the KEGG pathway database, and are listed in Table 2
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Fig3: The Entner-Doudoroff and the pentose phosphate pathways in H. boliviensis. Enzymes highlighted in blue were the subject of this study. Numbers and abbreviations for each metabolic step refer to the number of alleles and the cluster that the alleles formed with: P, Proteobacteria; B, bacteria; T, thermophilic archaea; A, non-thermophilic archaea and combinations of these groups of organisms. Database accession numbers for enzymes of H. boliviensis are provided in Table 2. EC numbers for the enzymes in the metabolisms are pointed out as classified in the KEGG pathway database, and are listed in Table 2

Mentions: The rate of consumption of glucose and maltose in the starch hydrolysate by H. boliviensis had distinctive patterns during both cell growth and polymer production (Fig. 2). The genome sequence of H. boliviensis was studied in order to determine the biochemical pathways in which these carbohydrates are assimilated. Enzymes involved in the Entner-Doudoroff (E-D) and pentose phosphate (PP) pathways were found to be involved (Fig. 3). Glucose is metabolized through the E-D pathway which initially involves two alleles of putative quinoprotein glucose dehydrogenases (E.C. 1.1.5.2), (Fig. 3, Table 2). A phylogenetic analysis of the protein sequences of these alleles revealed that they have diverged among enzymes of other Proteobacteria (Additional file 1: Figure S1). This phylogenetic cluster also included two alleles found in Halomonas sp. TD01 (Additional file 1: Figure S1); however the alleles in H. boliviensis did not share an evolutionary relationship with enzymes of H. elongata and C. salexigens (Additional file 1: Figure S1, Table 2). The E-D pathway in H. boliviensis continues with a gluconolactonase (E.C. 3.1.1.17) (Fig. 3) that formed a phylogenetic group with gluconolactonases belonging to bacteria not included among the Proteobacteria (Additional file 2: Figure S2, Table 2). Similar evolutionary analyses were performed on the remaining enzymes of the E-D pathway. Some of these enzymes have evolved along with enzymes of bacteria non-taxonomically related to H. boliviensis, and some enzymes have even diverged together with enzymes of archaea (Fig. 3).Fig. 3


Production of poly(3-hydroxybutyrate) by Halomonas boliviensis in an air-lift reactor.

Rivera-Terceros P, Tito-Claros E, Torrico S, Carballo S, Van-Thuoc D, Quillaguamán J - J Biol Res (Thessalon) (2015)

The Entner-Doudoroff and the pentose phosphate pathways in H. boliviensis. Enzymes highlighted in blue were the subject of this study. Numbers and abbreviations for each metabolic step refer to the number of alleles and the cluster that the alleles formed with: P, Proteobacteria; B, bacteria; T, thermophilic archaea; A, non-thermophilic archaea and combinations of these groups of organisms. Database accession numbers for enzymes of H. boliviensis are provided in Table 2. EC numbers for the enzymes in the metabolisms are pointed out as classified in the KEGG pathway database, and are listed in Table 2
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4522284&req=5

Fig3: The Entner-Doudoroff and the pentose phosphate pathways in H. boliviensis. Enzymes highlighted in blue were the subject of this study. Numbers and abbreviations for each metabolic step refer to the number of alleles and the cluster that the alleles formed with: P, Proteobacteria; B, bacteria; T, thermophilic archaea; A, non-thermophilic archaea and combinations of these groups of organisms. Database accession numbers for enzymes of H. boliviensis are provided in Table 2. EC numbers for the enzymes in the metabolisms are pointed out as classified in the KEGG pathway database, and are listed in Table 2
Mentions: The rate of consumption of glucose and maltose in the starch hydrolysate by H. boliviensis had distinctive patterns during both cell growth and polymer production (Fig. 2). The genome sequence of H. boliviensis was studied in order to determine the biochemical pathways in which these carbohydrates are assimilated. Enzymes involved in the Entner-Doudoroff (E-D) and pentose phosphate (PP) pathways were found to be involved (Fig. 3). Glucose is metabolized through the E-D pathway which initially involves two alleles of putative quinoprotein glucose dehydrogenases (E.C. 1.1.5.2), (Fig. 3, Table 2). A phylogenetic analysis of the protein sequences of these alleles revealed that they have diverged among enzymes of other Proteobacteria (Additional file 1: Figure S1). This phylogenetic cluster also included two alleles found in Halomonas sp. TD01 (Additional file 1: Figure S1); however the alleles in H. boliviensis did not share an evolutionary relationship with enzymes of H. elongata and C. salexigens (Additional file 1: Figure S1, Table 2). The E-D pathway in H. boliviensis continues with a gluconolactonase (E.C. 3.1.1.17) (Fig. 3) that formed a phylogenetic group with gluconolactonases belonging to bacteria not included among the Proteobacteria (Additional file 2: Figure S2, Table 2). Similar evolutionary analyses were performed on the remaining enzymes of the E-D pathway. Some of these enzymes have evolved along with enzymes of bacteria non-taxonomically related to H. boliviensis, and some enzymes have even diverged together with enzymes of archaea (Fig. 3).Fig. 3

Bottom Line: The largest amount of PHB, 41 % (wt.), was attained after 24 hrs of cultivation during which maltose in the hydrolysate was assimilated more rapidly than glucose during active cell growth; however, the rate of assimilation of both the carbohydrates was found to be similar during synthesis of PHB.Both maltose and glucose in the hydrolysate induce cell growth and PHB synthesis; most likely the cells balance adequately CoA and NAD(P)H during the assimilation of these carbohydrates.The combination of cheap substrates, simple production systems and the use of non-strict sterile conditions by the halophile H. boliviensis are desirable traits for large scale production of PHB, and should lead to a competitive bioprocess.

View Article: PubMed Central - PubMed

Affiliation: Center of Biotechnology, Faculty of Sciences and Technology, San Simon University, Cochabamba, Bolivia.

ABSTRACT

Background: Microbial polyesters, also known as polyhydroxyalkanoates (PHAs), closely resemble physical and mechanical features of petroleum derived plastics. Recombinant Escherichia coli strains are being used in industrial production of PHAs in Stirred Tank Bioreactors (STRs). However, use of Air-Lift Reactors (ALRs) has been known to offer numerous technical operating options over STRs, and as such has been successfully implemented in many bioprocesses. Halomonas boliviensis is a halophilic bacterium that is known to assimilate various carbohydrates and convert them into a particular type of PHA known as poly(3-hydroxybutyrate) (PHB). Owing to this capability, it has been used to synthesize the polyester using hydrolysates of starch or wheat bran in stirred tank bioreactors.

Results: This research article firstly describes the production of PHB in shake flasks by H. boliviensis using different combinations of carbohydrates and partially hydrolyzed starch as carbon sources. The highest PHB yields, between 56 and 61 % (wt.), were achieved when either starch hydrolysate or a mixture of glucose and xylose were used as carbon sources. The starch hydrolysate obtained in this study was then used as carbon source in an ALR. The largest amount of PHB, 41 % (wt.), was attained after 24 hrs of cultivation during which maltose in the hydrolysate was assimilated more rapidly than glucose during active cell growth; however, the rate of assimilation of both the carbohydrates was found to be similar during synthesis of PHB. An incomplete pentose phosphate pathway, which lacks 6-phosphogluconate dehydrogenase, was deduced from the genome sequence of this bacterium and may result in the characteristic assimilation of glucose and maltose by the cells.

Conclusions: This study showed that the production of PHB by H. boliviensis using cheap substrates such as starch hydrolysate in a simple production system involving an ALR is feasible. Both maltose and glucose in the hydrolysate induce cell growth and PHB synthesis; most likely the cells balance adequately CoA and NAD(P)H during the assimilation of these carbohydrates. The combination of cheap substrates, simple production systems and the use of non-strict sterile conditions by the halophile H. boliviensis are desirable traits for large scale production of PHB, and should lead to a competitive bioprocess.

No MeSH data available.


Related in: MedlinePlus