Growth dependent silencing and resetting of DGA1 transgene in Nannochloropsis salina

Here we report recombinant expression and activity of the Saccharomyces cerevisiae type 2 diacylglycerol acyltransferase DGA1 functioning in parallel with the native Nannochloropsis salina genes. Expression of DGA1 shifted the chain length distribution of fatty acids produced and reflected an oleoyl-CoA substrate preference. Effect on the total FAME content was moderate and elevated by a maximum of 38%. Expression of the DGA1 transgene varied throughout the culture life cycle and evidence of growth dependent environmental silencing of the transgene was observed. This is to our knowledge the first example of silencing and subsequent resetting in a transgenic microalga. Results from this study add valuable insights into the efficacy of algal genetic engineering and use of these microorganisms as bio-platforms for chemical manufacture.

Growth dependent silencing and resetting of DGA1 transgene in Nannochloropsis salina

Here we report recombinant expression and activity of the Saccharomyces cerevisiae type 2 diacylglycerol acyltransferase DGA1 functioning in parallel with the native Nannochloropsis salina genes. Expression of DGA1 shifted the chain length distribution of fatty acids produced and reflected an oleoyl-CoA substrate preference. Effect on the total FAME content was moderate and elevated by a maximum of 38%. Expression of the DGA1 transgene varied throughout the culture life cycle and evidence of growth dependent environmental silencing of the transgene was observed. This is to our knowledge the first example of silencing and subsequent resetting in a transgenic microalga. Results from this study add valuable insights into the efficacy of algal genetic engineering and use of these microorganisms as bio-platforms for chemical manufacture.

Co-production of bio-oil and propylene through the hydrothermal liquefaction of polyhydroxybutyrate producing cyanobacteria

A polyhydroxybutyrate (PHB) producing cyanobacteria was converted through hydrothermal liquefaction (HTL) into propylene and a bio-oil suitable for advanced biofuel production. HTL of model compounds demonstrated that in contrast to proteins and carbohydrates, no synergistic effects were detected when converting PHB in the presence of algae. Subsequently, Synechocystis cf. salina, which had accumulated 7.5wt% PHB was converted via HTL (15% dry weight loading, 340°C). The reaction gave an overall propylene yield of 2.6%, higher than that obtained from the model compounds, in addition to a bio-oil with a low nitrogen content of 4.6%. No propylene was recovered from the alternative non-PHB producing cyanobacterial strains screened, suggesting that PHB is the source of propylene. PHB producing microorganisms could therefore be used as a feedstock for a biorefinery to produce polypropylene and advanced biofuels, with the level of propylene being proportional to the accumulated amount of PHB.

Co-production of bio-oil and propylene through the hydrothermal liquefaction of polyhydroxybutyrate producing cyanobacteria

A polyhydroxybutyrate (PHB) producing cyanobacteria was converted through hydrothermal liquefaction (HTL) into propylene and a bio-oil suitable for advanced biofuel production. HTL of model compounds demonstrated that in contrast to proteins and carbohydrates, no synergistic effects were detected when converting PHB in the presence of algae. Subsequently, Synechocystis cf. salina, which had accumulated 7.5wt% PHB was converted via HTL (15% dry weight loading, 340°C). The reaction gave an overall propylene yield of 2.6%, higher than that obtained from the model compounds, in addition to a bio-oil with a low nitrogen content of 4.6%. No propylene was recovered from the alternative non-PHB producing cyanobacterial strains screened, suggesting that PHB is the source of propylene. PHB producing microorganisms could therefore be used as a feedstock for a biorefinery to produce polypropylene and advanced biofuels, with the level of propylene being proportional to the accumulated amount of PHB.