Metabolic pathway of 3,6-anhydro-L-galactose in agar-degrading microorganisms

Chang

2014

Biotechnol Bioproc E

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Recently, seaweeds have gained attention as possible renewable sources for biofuel and bioproduct production. To investigate the possibility of using green seaweeds as biomass feedstocks, the chemical composition and saccharification yield of the green seaweed Ulva pertusa were investigated. In this study, we evaluated U. pertusa that was harvested from the seashore in Jeju Island, Korea. By proximate composition analysis, dried U. pertusa was found to contain 52.3% carbohydrate, 25.1% protein, 0.1% lipid, and 22.5% ash. The elemental analysis of U. pertusa indicated the content of carbon to be 34.9%, hydrogen 5.3%, oxygen 46.5%, nitrogen 3.8%, sulfur 3.1%, and phosphorous 0.12%. The optimal conditions for the acid hydrolysis and saccharification of U. pertusa were investigated by varying the types of catalysts, catalyst concentration, reaction time, reaction temperature, and seaweed concentration. Under optimized acid hydrolysis condition, 32.9% of seaweed was recovered as monosaccharides and the monosaccharide composition was 11.5% D-glucuronic acid and D-glucuronic acid lactone, 11.1% L-rhamnose, 6.7% D-glucose, and 3.7% D-xylose. The concept of degree of reductance was introduced to assess the potential of U. pertusa as an industrial feedstock. It was found that the degree of reductance of U. pertusa was lowest among the biomass considered in this study. Based on the comparison of chemical composition and reductance degree of various biomass resources, the competitiveness of U. pertusa as a biomass feedstock for biofuel and bioproduct production was discussed.

Section: Degree Of Reductance Of U Pertusamentioning

confidence: 99%

Chemical composition, saccharification yield, and the potential of the green seaweed Ulva pertusa

Chang

2014

Biotechnol Bioproc E

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“…In these organisms, l-AnG and d-AnG are converted to 2-keto-3-deoxy-6-phospho-d-galactonate (d-KDPGal) through six and four enzyme-catalyzed reactions, respectively [see Figure 5 in Lee et al (2014Lee et al ( , 2016]. d-KDPGal enters the DeLey-Doudoroff pathway, where it is converted to the fermentable sugars glyceraldehyde-3-phosphate and pyruvate (Lee et al, 2014(Lee et al, , 2016. Glyceraldehyde-3-phosphate is then converted by glycolysis to pyruvate, which is metabolized to ethanol by alcoholic fermentation (Figures 3B,C).…”

Section: Microbial Fermentation Of 36-anhydro-galactoses To Ethanolmentioning

confidence: 99%

The Enzymatic Conversion of Major Algal and Cyanobacterial Carbohydrates to Bioethanol

2016

The production of fuels from biomass is categorized as first-, second-, or thirdgeneration depending upon the source of raw materials, either food crops, lignocellulosic material, or algal biomass, respectively. Thus far, the emphasis has been on using food crops creating several environmental problems. To overcome these problems, there is a shift toward bioenergy production from non-food sources. Algae, which store high amounts of carbohydrates, are a potential producer of raw materials for sustainable production of bioethanol. Algae store their carbohydrates in the form of food storage sugars and structural material. In general, algal food storage polysaccharides are composed of glucose subunits; however, they vary in the glycosidic bond that links the glucose molecules. In starch-type polysaccharides (starch, floridean starch, and glycogen), the glucose subunits are linked together by α-(1→4) and α-(1→6) glycosidic bonds. Laminarin-type polysaccharides (laminarin, chrysolaminarin, and paramylon) are made of glucose subunits that are linked together by β-(1→3) and β-(1→6) glycosidic bonds. In contrast to food storage polysaccharides, structural polysaccharides vary in composition and glycosidic bond. The industrial production of bioethanol from algae requires efficient hydrolysis and fermentation of different algal sugars. However, the hydrolysis of algal polysaccharides employs more enzymatic mixes in comparison to terrestrial plants. Similarly, algal fermentable sugars display more diversity than plants, and therefore more metabolic pathways are required to produce ethanol from these sugars. In general, the fermentation of glucose, galactose, and glucose isomers is carried out by wild-type strains of Saccharomyces cerevisiae and Zymomonas mobilis. In these strains, glucose enters glycolysis, where is it converted to pyruvate through either Embden-Meyerhof-Parnas pathway or Entner-Doudoroff pathway. Other monosaccharides must be converted to fermentable sugars before entering glycolysis. In contrast, microbial wild-type strains are not capable of producing ethanol from alginate, and therefore the production of bioethanol from alginate was achieved by using genetically engineered microbial strains, which can simultaneously hydrolyze and ferment alginate to ethanol. In this review, we emphasize the enzymatic hydrolysis processes of different algal polysaccharides. Additionally, we highlight the major metabolic pathways that are employed to ferment different algal monosaccharides to ethanol.

“…We used two agarose-hydrolyzing enzymes for the production of L-AnG; an exo-type β-agarase (Patl_1971) to produce neoagarobiose from agarose and a neoagarobiose hydrolase (SCO3481) to produce L-AnG from neoagarobiose [17]. We selected these enzymes after testing various combinations of endo-and exo-type β-agarases and neoagarobiose hydrolases obtained from P. atlantica, S. coelicolor A3(2), and P. marina M091.…”

Section: Preparation Of Agarose-hydrolyzing Enzymesmentioning

confidence: 99%

“…The phylogenetic analysis of the 16S rRNA of P. marina M091 showed that it belongs to the class Flavobacteria in the phylum Bacteroidetes. We also carried out a genomic analysis of this microorganism to search for genes involved in L-AnG metabolism [17].…”

Section: Introductionmentioning

confidence: 99%

“…We also compared the substrate and cofactor specificities of the L-AnGDHs obtained from the marine bacterium P. marina (Pm_L-AnGDH) and the soil bacterium Streptomyces coelicolor (Sc_L-AnGDH). Unlike P. marina, which are gram-negative marine bacteria, S. coelicolor A3(2), which can degrade and utilize agar as the sole carbon source, is a gram-positive soil bacterium of the class Actinobacteria in the phylum Actinobacteria [17]. Phylogenetic analysis showed that Sc_L-AnGDH and Pm_L-AnGDH formed a separate cluster.…”

Section: Introductionmentioning

confidence: 99%

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Identification and characterization of 3,6-anhydro-L-galactose dehydrogenases belonging to the aldehyde dehydrogenase superfamily from marine and soil microorganisms

Cho

2014

Biotechnol Bioproc E

Self Cite

The complete hydrolysis of agarose produces its monomeric sugars, D-galactose and 3,6-anhydro-Lgalactose (L-AnG). Although enzymes of D-galactose metabolism are well characterized, those involved in L-AnG metabolism have not yet been investigated. In this study, we report the identification and characterization of L-AnG dehydrogenase (L-AnGDH), an aldehyde dehydrogenase (ALDH), catalyzing the first step of L-AnG degradation. To compare substrate and cofactor specificities of L-AnGDH, two L-AnGDH genes obtained from the marine bacterium Postechiella marina (Pm_L-AnGDH) and the soil bacterium Streptomyces coelicolor (Sc_L-AnGDH) were cloned and expressed in E. coli. Whereas the recombinant Pm_L-AnGDH and Sc_L-AnGDH were similar in their oligomeric state (homotetramer) and optimum reaction conditions (30°C, pH 8.0), the two enzymes were distinguishable by their substrate and cofactor specificities. Sc_L-AnGDH catalyzed the oxidation of L-AnG using both NAD + and NADP + , with a preference for NAD + . It also catalyzed the dehydrogenation of L-glyceraldehyde, glycolaldehyde, and L-lactaldehyde in the presence of NAD + . On the other hand, Pm_L-AnGDH showed exclusive selectivity towards NADP + and did not oxidize aldehydes other than L-AnG and L-glyceraldehyde. The phylogenetic analysis of amino sequences indicated that L-AnGDH belongs to a novel subfamily within the ALDH superfamily. To our knowledge, this is the first report on the characterization of L-AnGDH.