Integrated bioprocesses to increase the sustainability of biofuels production from microalgae biomass

DO NASCIMENTO M; SANCHEZ RIZZA L.; ARRUEBARRENA A.; CURATTI L.

Mar del Plata

Congreso; X Congreso Argentino de Microbiología General; 2014

SAMIGE

Production of biofuels from microalgae biomass, although very promising, is not commercially available yet. This is mostly because production costs are still too high in comparison with petroleum and primary products of agriculture as feedstocks for first-generation biofuels. Similar to intensive agriculture, one of the drawbacks of implementing massive cultivation of microalgae is the unsustainable requirements of fertilizers, especially N. Microalgae have an average composition of CH1,7O0,4N0,15P0,0094, with N accounting for 4 to 8% on a dry biomass basis, making the bioprocess considerably more N-intensive than traditional agriculture.It is presumed that the development of breakthrough technologies for integrated bioprocesses comprising a multiplicity of microorganism that allow nutrients recycling and co-production of high value by-product would be necessary to realize the potential of microalgae biomass for bioenergy, food, feed and biomaterials. In this work we show the production of cyanobacterial biomass at the expense of N from the air. Upon rehydration of dry biomass highly concentrated cell-free extracts could be obtained. This extracts were highly enriched in the proteinaceous pigments phycoerytrin and phycocianin that could be purify using simple biochemical techniques. Additionally, this cell-free extracts proved to be a suitable source of nitrogen for the cultivation of many oleaginous microalgae. Moreover, the extracts sustain the algae growth without the need of additional nutrients. Proteins in the cell-free extracts were converted into Chlorella sorokiniana biomass with an efficiency close to 100 %. Control experiments show that while C. sorokiniana is able to use short peptides (trypteine) as a sole nitrogen source, it failed to use proteins such as bovine serum albumin or casein, suggesting it does not make use of extracellular proteases to degrade these substrates. Then, by means of an artificial substrate for proteases (azo-casein) we determined that the proteins in the cell-free extracts were degraded by proteases of cyanobacterial origin at a rate that did not impose a nutrient deficit to the microalgae. Interestingly, algae cells fed with cyanobacterial cell-free extracts presented a 60% increase in the accumulation of neutral lipids up to 35 % (w/w) on a dry biomass basis. The resulted oleaginous biomass had a similar fatty acids profile that microalgae cultivated in mineral medium and would represent a suitable feedstock for biodiesel production.These results show a prototype of a multispecies biorefinery that make use of inexpensive and abundant nutrients (CO2 and N2), that allow highly efficient biomass recycling and the co-purification of high value by-products.