Co-production of single cell oil and gluconic acid using oleaginous Cryptococcus podzolicus DSM 27192

Abstract

Background The co-production of single cell oil (SCO) with value-added products could improve the economic viability of industrial SCO production. The newly isolated oleaginous yeast Cryptococcus podzolicus DSM 27192 was able to co-produce SCO intracellularly and gluconic acid (GA) extracellularly. In this study, the metabolic regulation of carbon distribution between SCO and GA through process optimization was comprehensively investigated. Results The carbon flow distribution between SCO and GA was significantly influenced by the cultivation conditions, such as nitrogen sources, glucose concentration and dissolved oxygen concentration. It was found that organic nitrogen sources were beneficial for SCO accumulation, while GA production was decreased. Dissolved oxygen concentration (DOC) was found to enhance SCO accumulation, while high glucose concentration was more favorable for GA accumulation. Hence, a two-stage DOC or glucose concentration-controlled strategy was designed to improve cell growth and direct carbon distribution between SCO and GA. Moreover, C. podzolicus DSM 27192 could degrade its stored lipids to synthesize GA in the late stationary phase, although considerable amounts of glucose remained unconsumed in the culture medium, indicating the importance of fermentation time control in co-production systems. All these observations provide opportunity to favor either the production of SCO or GA or rather their simultaneous production. Conclusions Co-production of SCO and GA by C. podzolicus DSM 27192 can improve the economical value for microbial lipid-derived biodiesel production. Moreover, the results of the proposed co-production strategy might give guidance for other co-production systems.

Evaluation of Downstream Processing, Extraction, and Quantification Strategies for Single Cell Oil Produced by the Oleaginous Yeasts Saitozyma podzolica DSM 27192 and Apiotrichum porosum DSM 27194

“…Within this study a higher SCO production potential of the yeast S. podzolica is proven, compared to the previous studies performing only DT with this yeasts' biomass (Schulze et al, 2014;Qian et al, 2019Qian et al, , 2020. Moreover, the downstream process using HPH and ethanol-hexane extraction prior to transesterification is not only more efficient but also more energy saving than DT.…”

“…In this study, we evaluate combinations of cell disruption and extraction methods on two by Schulze et al (2014) isolated oleaginous yeasts, Saitozyma podzolica DSM 27192 and Apiotrichum porosum DSM 27194. These unconventional yeasts have been recently characterized as co-producer of intracellular SCO and extracellular gluconic acid, when cultivated on glucose (Schulze et al, 2014;Qian et al, 2019). Additionally, Qian et al (2020) demonstrated that both yeasts are robust SCO producers capable of using the cheap industrial by-product acetate.…”

“…(physico-chemical treatment by heat and alkali or acid), which serve as control as it was the only lipid determination method in previous upstream studies (Schulze et al, 2014;Qian et al, 2019Qian et al, , 2020. The derivatization to FAME directly serves the purpose to produce biodiesel (Li et al, 2008;Sathish et al, 2014;Yousuf et al, 2017), whereas valuable FFA can be applied as nutritional supplements (Whigham et al, 2000;Smedman and Vessby, 2001;Kim et al, 2016).…”

Optimization of carbon source efficiency for lipid production with the oleaginous yeast Saitozyma podzolica DSM 27192 applying automated continuous feeding

“…After a response surface aimed methodology (data not shown) the tendencies of optimal parameters were directed to 22.5 °C and pH 4. Since basic knowledge about carbon source and sugar concentration [ 20 , 23 ] was present, this response surface methodology dealt with yet unknown parameters, namely temperature, pH and agitation. For agitation it was observed that the 600 rpm of the standard process were already optimal.…”

“…Too high sugar concentrations are not only uneconomical, but can rather lead to narrow productivity, due to substrate inhibition. It is known, however, that S. podzolica is able to tolerate high glucose concentrations of up to 150 g/L for lipid production, although inhibiting effects on cell propagation were observed, which consequently decreased the lipid titer [ 23 ]. Therefore, resulting from this study, for lipid production with S. podzolica high C/N ratio in the batch phase is mandatory, however, once nitrogen is limited the excess sugar concentration of 10 g/L ensured stable productivities, as can be seen in Fig.…”