Direct Production of Biodiesel from the Fungus M. circinelloides; Opportunity to Enhance Yield with Genetic Engineering

. circinelloides , the team determined that an acid-catalyzed process was more suitable for producing biodiesel than an alkali one to avoid yield losses from free fatty acid neutralization.

They used the acid-catalyzed direct transformation
method with methanol and chloroform as solvents and H₂SO₄, HCl, and BF₃ as acid catalysts. Using optimal reaction conditions (8 h at 65 °C), biodiesel yields were 18.9, 18.9, and 18.4% relative to the dry
mass of M. circinelloides, using H₂SO₄, HCl, and BF₃,
respectively.

These yields were even slightly higher than the corresponding theoretical yield calculated for this microorganism (18.1%), indicating that acid-catalyzed direct transesterification/esterification of fungal biomass can be applied to M. circinelloides biomass from submerged cultures because it improves the amount of total lipids extracted in comparison to the conventional methods for lipid extraction from microorganisms.

This observation is supported by previous works describing increased recovery of fatty acids from microorganisms by direct transesterification techniques. Interestingly, these results also indicate that saponifiable lipids other than triglycerides, such as phospholipids, sphingolipids, and saccharolipids, are transformed into FAMEs by this method and should be considered
as substrates for FAME obtention.

…biodiesel yields should be increased to make the industrial process economical, which could be attained by the genetic manipulation of this fungus. In this sense, efforts are now dedicated to overexpress genes that code
for enzymes postulated to be rate-limiting steps for fatty
acid biosynthesis in oleaginous fungi. Other strategies are
focused on the generation of strains with enhanced ability to
use crop residues or industrial byproduct, avoiding competition
with the food supply, with low linolenic acid levels or
overexpressing genes involved in saponifiable lipid biosynthesis.

Particularly interesting is the generation of strains with
low free fatty acid levels because they could be used for
biodiesel production by using a base-catalyzed technology,
which is the common way to produce biodiesel on an industrial
scale.

—Vicente et al.

Resources

• Gemma Vicente et al. (2010) Direct Transformation of Fungal Biomass from Submerged Cultures into Biodiesel. Energy Fuels, Article ASAP doi: 10.1021/ef9015872