PEER-REVIEWED ARTICLE bioresources.com Dygas et al. (2022). “Yeast on rapeseed hydrolysates,” BioResources 17(2), 3082-3094. 3082 Conventional and Unconventional Yeasts Able to Grow on Rapeseed Meal Hydrolysates Dawid Dygas,* Paulina Janicka, Joanna Berłowska, and Dorota Kręgiel * Yeast strains and appropriate hydrolysis conditions were selected for efficient single cell protein (SCP) production from waste rapeseed meal. High potential for effective biomass production was observed for Yarrowia lipolytica LOCK0264 with 10 g of rapeseed meal at 4.9 × 10 8 ± 1.5 × 10 8 (2.91 logarithmic units). The highest yeast multiplication rate was obtained for Metschnikowia pulcherrima NCYC747 with 12.5 g of rapeseed meal and with 15 g of rapeseed meal at 1.6 × 10 8 ± 3.8 × 10 7 and 4.5 × 10 8 ± 4.0 × 10 7 (2.75 and 2.86 logarithmic units, respectively). DOI: 10.15376/biores.17.2.3082-3094 Keywords: Rapeseed meal; Enzymatic hydrolysis; Unconventional yeasts Contact information: Department of Environmental Biotechnology, Lodz University of Technology, 90-924 Lodz, Poland; *Corresponding authors: dorota.kregiel@p.lodz.pl; dawid.dygas@dokt.p.lodz.pl INTRODUCTION Rapeseed (Brassica napus) is widely used for oil production across the world. Global production of rapeseed oil reached 27.3 million metric tons in 2019 and 2020. The main provider of rapeseed meal was Canada, at 19 million metric tons. The second largest producer was the European Union, at 16.8 million metric tons. The third was China at 7 million metric tons (Shahbandeh 2021). Rapeseed oil has a high content of vitamins and unsaturated fatty acids and is especially valuable in the food and cosmetics industries. Rapeseed oil may also be used as an additive in diesel fuel or as an independent fuel (Zentková and Cvengrošová 2013; Paciorek-Sadowska et al. 2019). The by-product from the production of rapeseed oils is pomace (sometimes referred to as oil cake or rapeseed meal). Currently, the most important application of pomace is for the production of animal feed. Rapeseed meal is a good source of nutritional components, with a high content of methionine and lower content of lysine and isoleucine. Lysine is one of the most important amino acids and is a growth-limiting factor. In comparison to soybean meal, the essential amino acids present in rapeseed meals show lower digestibility. Rapeseed meal contains about 31.6% of neutral detergent fiber, which is about three times more than soybean meal (10.5%). Rapeseed oil contains far more acid detergent fiber (20.7% vs. 5.7%) and lignin (9.7% vs. 0.4% of dry matter) than soybean meal (Table 5). The digestibility of lignin is limited, and this can affect the digestive tract, energy release, and animal growth. In broiler production, excessive ingestion of rapeseed meal produces an off-fishy flavor in eggs. Another problem is increased cases of liver hemorrhaging. Rapeseed meal contains many anti-nutritional substances, such as glucosinolates, phytates, erucic acid, and alkaloids (Bau et al. 1994; Mandiki et al. 2002). Generally, glucosinolates are not toxic. However, their derivatives can have side effects on the liver, kidneys, and thyroid. Damage to the thyroid gland occurs via disturbance of iodine metabolism (Grubb