Lipid Production from Amino Acid Wastes by the Oleaginous Yeast Rhodosporidium toruloides

Abstract

Microbial lipids have been considered as promising resources for the production of renewable biofuels and oleochemicals. Various feedstocks, including sugars, crude glycerol, and volatile fatty acids, have been used as substrates for microbial lipid production, yet amino acid (AA) wastes remain to be evaluated. Here, we describe the potential to use AA wastes for lipid production with a two-stage culture mode by an oleaginous yeast strain Rhodosporidium toruloides CGMCC 2.1389. Each of the 20 proteinogenic AAs was evaluated individually as sole carbon source, with 8 showing capability to facilitate cellular lipid contents of more than 20%. It was found that L-proline was the most favored AA, with which cells accumulated lipids to a cellular lipid content of 37.3%. When blends with AA profiles corresponding to those of meat industry by-products and sheep viscera were used, the cellular lipid contents reached 27.0% and 28.7%, respectively. The fatty acid compositional analysis of these lipid products revealed similar profiles to those of vegetable oils. These results, thus, demonstrate a potential route to convert AA wastes into lipids, which is of great importance for waste management and biofuel production.

Exogenous l-proline improved Rhodosporidium toruloides lipid production on crude glycerol

“…Among others, the oleaginous yeasts are considered as potential lipid producers due to their higher growth rate, adaptation to diverse substrates, and higher lipid production yields. Until now, various organic substrates including waste cooking oils [ 8 ], different biomass derived sugars [ 9 ], amino acid-rich wastes [ 10 ], and industrially produced organic wastes [ 11 ], have been utilized for microbial lipid production. However, the high production cost of microbial lipid technology prevent its broader commercialization [ 12 ], where the fermentation processes and substrate costs are significant to lipid production [ 13 ].…”

Co‐utilization of amino acid‐rich wastes and glycerol for microbial lipid production

“…1). We previously demonstrated successful lipid production with AA blends matching a similar AA compositional profile to sheep viscera AA (SVAA), 35 fish muscle AA (FMAA), 36 or meat industry by-product AA (MIAA), 37 as carbon substrates; 23,24 however, it was found that AA in high concentrations had adverse effects on cell viability and lipid production, which might have been due to the high osmotic stress, high intracellular AA level, 42 accumulation of ammonia or inhibitory metabolic intermediates, 43,44 or the very low C/N ratio of the media, as the C/N ratio of about 100 was found to be favorable for lipid production. 21,22 To improve the C/N ratio of the media and subsequently encourage microbial lipid production on AA, 20 g L -1 glycerol was supplied to the media containing the designated AA blends with similar AA compositions to SVAA, FMAA, and MIAA, respectively (Table 1).…”

“…Glycerol addition improved the lipid production and maintained relatively high cell mass compared with our previous results using FMAA blends for lipid production. 23,24 The highest AA consumption of 37.1 g L -1 (61.5%) was observed using MIAA with 8.8 g L -1 (44.2%) glycerol consumption. The C/N ratio of 5.2 was relatively high compared with other AA blends but the low lipid yield of 6.9 g 100 g -1 might have been due to the high substrate concentration in the media (Table 2, entry 3).…”

“…21,22 In fact, the issue of low C/N ratios can be solved by applying two-stage culture conditions, 18 or supplying additional carbon sources to increase the C/N ratio of the media. 17 Our previous studies revealed encouraging results using AAs as a substrate for microbial lipid production; 23,24 however, to improve the lipid production with AAs, supplying additional carbon sources might further benefit the process. About 10% of crude glycerol is generated as a by-product during the process of biodiesel production, which produces several impurities that are at risk of disposal.…”

Rhodosporidium toruloides - A potential red yeast chassis for lipids and beyond

“… 2010 ; Li et al . 2020 ). To accumulate high amounts of lipids, oleaginous yeasts are usually cultivated under nitrogen-limited conditions (Evans and Ratledge 1984 ).…”