Method for producing single cell oil from lignocellulosic materials
The present disclosure relates to methods for producing microbial lipids. The present disclosure also relates to methods for producing microbial lipids using inhibitors obtainable from lignocellulosic materials to suppress the proliferation of unwanted microorganisms in the fermentation broth. The method can therefore reduce the risk of having contaminating microbes establish in the system and the cultivation and thus higher yields of microbial lipids may be obtained.
1. A method for producing lipids, comprising:
(i) providing a cultivation medium having a lignocellulosic hydrolysate,
(ii) providing a fermentation broth by inoculating the cultivation medium of (i) with a first microbe, where said first microbe is an oleaginous microbe,
(iii) incubating said medium inoculated with said first microbe to allow lipids to accumulate, wherein said fermentation broth includes at least one microbial growth inhibitor, and wherein said first microbe is tolerant to said microbial growth inhibitor(s), wherein said incubation is conducted under aerobic conditions,
(iv) adding said at least one microbial growth inhibitor or adjusting the concentration of said at least one microbial growth inhibitor in the fermentation broth, wherein said fermentation broth comprises a second non-oleaginous microbe which is intolerant to said at least one microbial growth inhibitor, whereas said microbial growth inhibitor is present in said fermentation broth at a concentration within a range of tolerance of said first microbe and outside a range of tolerance of said second microbe,
(v) collecting accumulated lipids.
2. The method according to claim 1 , wherein said second microbe is present in the cultivation medium provided in step (i) or contaminated the fermentation broth at step (ii) or (iii).
3. The method according to claim 1 , wherein at least one microbial growth inhibitor is a phenolic compound measured as concentration of total phenols per volume of fermentation broth.
4. The method according to claim 3 , wherein a level of said phenolic compound in said fermentation broth is at least 1 g/l.
5. The method according to claim 3 , wherein a level of said phenolic compound in said fermentation broth is in a range of 1 g/l to 7 g/l or above.
6. The method according to claim 3 , wherein a level of said phenolic compound in said fermentation broth is within a range of 1 g/l to 5 g/l.
7. The method according to claim 1 , wherein said first microbe is selected from the group consisting of: filamentous fungi, yeast, bacteria and algae.
8. The method according to claim 1 , wherein said first microbe is selected from the group consisting of: Mortierella, Aspergillus, Lipomyces, Rhodosporidium and Cryptococcus.
9. The method according to claim 1 , wherein said second microbe is non-oleaginous selected from the group consisting of: bacteria, yeast, filamentous fungi or microalgae.
10. The method according to claim 1 , wherein said second microbe is a bacterium selected from the group consisting of: Bacillus spp., Pseudomonas spp.
11. The method according to claim 1 , wherein said first microbe is selected for producing and accumulating more than fifteen percent of its weight as lipid.
12. The method according to claim 3 , wherein a level of said phenolic compound in said fermentation broth is within a range of 1 g/l to 3 g/l.