Vol.:(0123456789) 1 3 Biomass Conversion and Biorefinery https://doi.org/10.1007/s13399-021-01600-z ORIGINAL ARTICLE Purifcation of biodiesel‑derived crude glycerol by acidifcation to be used as a carbon source for microbial oil production by oleaginous yeast Pseudozyma parantarctica CHC28 Chutima Rakkitkanphun 1  · Jantima Teeka 1,2  · Dolnapa Kaewpa 1,2  · Atsadawut Areesirisuk 1,2 Received: 19 March 2021 / Revised: 15 May 2021 / Accepted: 18 May 2021 © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021 Abstract This research aimed to apply the acidifcation method to remove impurities from biodiesel-derived crude glycerol (BCG) and investigate the potential of purifed BCG (PBCG) to be used as a carbon source for microbial oil production by oleaginous yeast Pseudozyma parantarctica CHC28. The optimum purifying conditions of BCG were pretreated with hydrochloric acid at a pH of 1.71. The PBCG concentration was 469.52 g/L under optimized conditions. The batch fermentation was studied using a nitrogen-limited medium containing PBCG (PBCG-medium). The PBCG-medium with 50 g of PBCG per liter provided the maximum biomass and oil concentration of 11.10 g/L and 4.07 g/L, respectively. The oil accumulation was approximately 45%. The long-chain fatty acids C16–C18 were the main compositions, which accounted for over 85%. These results suggested that the conversion of PBCG into microbial oil was an interesting direction to produce microbial oil. It was also a remarkable solution to add value to the by-products from biodiesel production. The mathematical model was demonstrated to describe satisfactorily the yeast growth and microbial oil production profle achieved in media containing pure glycerol and PBCG as carbon sources. Keywords Purifcation · Optimization · Biodiesel-derived crude glycerol · Microbial oil · Pseudozyma parantarctica · Mathematical modeling 1 Introduction With growing fuel shortage and environmental issues, renew- able fuels are gaining prominence in meeting rising energy demand and avoiding environmental issues. Biofuel is a renewable, biodegradable, non-polluting fuel that does not extend net CO 2 in the atmosphere [1]. Biodiesel is a renewa- ble biofuel produced by the transesterifcation of triglycerides in oils and fats with short-chain alcohols and a suitable cata- lyst. The crude glycerol is a major by-product of the transes- terifcation process. It is estimated that approximately 0.1 ton of crude glycerol can be obtained per 1 ton of biodiesel [2]. The biodiesel-derived crude glycerol (BCG) obtained from the transesterifcation reaction generally has low purity. The compositions of BCG are according to the conversion meth- ods, type of alcohol, and inducing catalyst. BCG also contains excessive alcohol, used catalyst, and soap residue, resulting in a substance with limited applications and low commercial value, and is thus typically discarded as waste in landflls [3, 4]. Previously, the purifed crude glycerol was used in various biological applications such as food industries, animal food, pharmaceutical products, polymer, cosmetics, and carbon sources in the fermentation process [5–7]. For the bioconver- sion processes, contaminants in BCG pose some problems, such as plugging the bioreactor, disabling the catalysts, and inhibiting microbial activities. Therefore, the BCG needs to be purifed to remove the impurities and increase glycerol content before applying it for the above purposes. Diferent glycerol purifcation methods are developed to increase the yield of processes and practices in industrial operations. The ion exchange resin and simple distillation provide a very low glycerol yield [8]. The nano-cavitation technology is an exciting process, but it is not practical in large-scale operation [9]. The membrane separation method * Atsadawut Areesirisuk atsadawut_a@rmutt.ac.th 1 Division of Biology, Faculty of Science and Technology, Rajamangala University of Technology, Thanyaburi 12110, Pathum Thani, Thailand 2 Center of Excellence in Nano-Biotechnology, Faculty of Science and Technology, Rajamangala University of Technology, Thanyaburi 12110, Pathum Thani, Thailand