Polyunsaturated fatty acids (PUFAs) are essential in healthy diets and their production is extremely important. Natural sources of PUFAs includes animal and aquatic products such as marine fish oil, however there are several limitations such as the decrease of fish stocks throughout the world. Thus, microbial oils are a preferable source of PUFAs. Herein, it was studied the production of PUFAs by Mortierella alpina under solid-state fermentation (SSF) using polyurethane foam as inert substrate and synthetic medium or lignocellulosic hydrolysate as source of C, N, and other nutrients. Several parameters of fermentation conditions were evaluated as carbon source, inductors addition, ratio C/N and temperature. The highest amount of total PUFAs per mass of solid (535.41 ± 24.12 mg/g), linoleic acid (129.66 ± 5.84 mg/g), and α-linoleic acid (401.93 ± 18.10 mg/g) were produced when the culture medium contained 20 g/L glucose, 10% (w/v) linseed oil, the C/N ratio was adjusted to 25 and the incubation temperature was 25 C for 3 days decreasing to 16 C on the remaining 4 days of fermentation. In addition, a hemicellulosic hydrolysate can be used as low-cost substrate to produce PUFAs, although the production was lower than the achieved with synthetic medium. SSF showed an interesting technology for microbial PUFAs production.Polyunsaturated fatty acids (PUFAs) are essential compounds that can be found in fish, vegetal oil, flax seeds, walnuts, and some types of vegetables. 1 PUFAs play an important role in the diet due to health benefits, specially the ω-3 class such as eicosapentaenoic acid (EPA or C20:5n-3), α-linolenic acid (ALA or C18:3n-3) and docosahexaenoic acid (DHA or C22:6n-3) and of the ω-6 class, like arachidonic acid (ARA or C20:4n-6), γ-linoleic acid (GLA or C18:3n-6), linoleic acid (LA or C18:2n-6), and conjugated linolenic acid (CLA). 2 They are structural components of the membrane phospholipids and precursors of the eicosanoids (hormone-like substances that influence the immune, cardiovascular and central nervous systems, such as prostaglandins, thromboxanes, and leukotrienes). Furthermore, PUFAs are present in the cerebral cortex, retina and are components of immunocompetent cells like neutrophils and monocytes. In humans PUFAs are not synthesized in sufficient amounts within the body, so they should be ingested from food sources. 3,4 In the food industry, lipids rich in PUFAs are highly demanded and used as food additives to improve and/or supplement the fatty acid composition of specific foods such as infant food.Other sources of PUFAs are based on microbial fermentation processes. The accumulation of PUFAs by microorganisms has various advantages compared with animal or plant sources, because it is independent from location, climate and season, does not require the use of arable land and microorganisms can be cultivated in various types