Improved fed-batch processes with Wickerhamomyces anomalus WC 1501 for the production of d-arabitol from pure glycerol

Abstract

Background d-Arabitol, a five-carbon sugar alcohol, represents a main target of microbial biorefineries aiming to valorize cheap substrates. The yeast Wickerhamomyces anomalus WC 1501 is known to produce arabitol in a glycerol-based nitrogen-limited medium and preliminary fed-batch processes with this yeast were reported to yield 18.0 g/L arabitol. Results Fed-batch fermentations with W. anomalus WC 1501 were optimized using central composite design (CCD). Dissolved oxygen had not a significant effect, while optimum values were found for glycerol concentration (114.5 g/L), pH (5.9), and temperature (32.5 °C), yielding 29 g/L d-arabitol in 160 h, a conversion yield of 0.25 g of arabitol per g of consumed glycerol, and a volumetric productivity of 0.18 g/L/h. CCD optimal conditions were the basis for further improvement, consisting in increasing the cellular density (3✕), applying a constant feeding of glycerol, and increasing temperature during production. The best performing fed-batch fermentations achieved 265 g/L d-arabitol after 325 h, a conversion yield of 0.74 g/g, and a volumetric productivity of 0.82 g/L/h. Conclusion W. anomalus WC 1501 confirmed as an excellent producer of d-arabitol, exhibiting a remarkable capability of transforming pure glycerol. The study reports among the highest values ever reported for microbial transformation of glycerol into d-arabitol, in terms of arabitol titer, conversion yield, and productivity. Graphical Abstract

Production of arabitol from glycerol by immobilized cells of Wickerhamomyces anomalus WC 1501

“…However, in these conditions, glycerol utilization likely contributed to the growth of planktonic cells, which reached an OD 600 of 38.0, while arabitol production was depressed in terms of final titre (4.6 g/L), yield and productivity ( p < 0.05). This observation confirms the importance of inorganic nitrogen limitation for W. anomalus WC 1501 likewise in other yeasts ( Nozaki et al, 2003 ; Filippousi et al, 2019 ; Filippousi et al, 2022 ; Raimondi et al, 2022 ). Nonetheless, the mechanism of such regulation (e.g., a potential role of AMP deaminase as in oleaginous fungi) remains to be clarified in W. anomalus .…”

“…A recent study indicated that the production of arabitol is triggered by nitrogen limitation also in Y. lipolytica ( Vastaroucha et al, 2024 ), but the conflicting evidence, that arabitol production by this species is growth associated and necessitates a supply of ammonium, also exists in the literature ( Yang et al, 2021 ). The non-growth-associated nature of production was exploited in a successful fed-batch process, where W. anomalus WC 1501 was first allowed to grow, and then arabitol production was induced with a pulse and feeding of concentrated glycerol ( Raimondi et al, 2022 ). In this study, the feasibility of the process was explored by utilizing pre-produced cells of W. anomalus WC 1501 that were immobilized in AB and brought into contact with a medium containing a high concentration of glycerol.…”

“…The yeast strain W. anomalus WC 1501, belonging the collection of the Laboratory of Microbial Biotechnologies (Department of Life Sciences, University of Modena and Reggio Emilia) and already known for its ability to produce arabitol from glycerol ( Raimondi et al, 2022 ), was routinely cultured in MY medium [20 g/L glycerol, 3 g/L yeast extract, 2 g/L (NH 4 ) 2 SO 4 , 3 g/L KH 2 PO 4 , 1 g/L K 2 HPO 4 , and 1 g/L MgSO 4 · 7H 2 O], where the yeast was incubated aerobically at 30°C for 24 h. Unless otherwise stated, arabitol production was carried out in MY medium containing 120 g/L glycerol, with any modifications necessary for specific experiments being explicitly indicated.…”

“…Nevertheless, the presently reported yields and titers remain below the competitive values required for industrial-scale applications, thus limiting the bioconversion of arabitol from glycerol to laboratory scale. A recent study by Raimondi et al (2022) demonstrated promising results, reporting high values of yield (Y P/S ) and arabitol titer using the strain Wickerhamomyces anomalus WC 1507 in a fed-batch process with synthetic medium and glycerol as the sole carbon source.…”

Fermentative processes for the upcycling of xylose to xylitol by immobilized cells of Pichia fermentans WC1507

“…Due to the substantial carbohydrate content, LCB represents a valuable source of fermentable sugars like glucose, arabinose, mannose, and xylose, as well as aromatic compounds. LCB could provide numerous industrially relevant molecules generated by biorefineries, among which sugar alcohols such as xylitol and arabitol have been recognized as top value-added chemicals and have garnered increasing scientific attention ( Werpy and Peterson, 2004 ; Erickson et al, 2012 ; Raimondi et al, 2022 ).…”