Efficient simultaneous production of extracellular polyol esters of fatty acids and intracellular lipids from inulin by a deep-sea yeast Rhodotorula paludigena P4R5

Abstract

Background Polyol esters of fatty acids (PEFA) are a kind of promising biosurfactants and mainly secreted by Rhodotorula strains. In addition, some strains of Rhodotorula are reliable producers of microbial lipid. Therefore, it is feasible to establish a one step fermentation process for efficient simultaneous production of PEFA and microbial lipids by a suitable Rhodotorula strain. Results A newly isolated deep-sea yeast, Rhodotorula paludigena P4R5, was shown to simultaneously produce high level of intracellular lipid and extracellular PEFA. Under the optimized conditions, it could yield 48.5 g/L of PEFA and 16.9 g/L of intracellular lipid within 156 h from inulin during 10-L batch fermentation. The PEFA consisting of a mixture of mannitol esters of 3-hydroxy C 14 , C 16 and C 18 fatty acids with variable acetylation showed outstanding surface activity and emulsifying activity, while the fatty acids of the intracellular lipid were mainly C 16 and C 18 and could be high-quality feedstock for biodiesel production. Conclusion The deep-sea yeast strain R. paludigena P4R5 was an excellent candidate for efficient simultaneous of biosurfactants and biodiesel from inulin. Our results also suggested that the establishment of fermentation systems with multiple metabolites production was an effective approach to improve the profitability.

Genomics- and Metabolomics-Based Investigation of the Deep-Sea Sediment-Derived Yeast, Rhodotorula mucilaginosa 50-3-19/20B

“…It is a member of glycoside hydrolase family 32 (GH32) with a size of 71.24 kDa and harbors conserved protein sequence motifs with the catalytic triad ( 192 D-316 D-366 E). Previous studies reported this enzyme also in other fungi identifying the well-known sequence signatures and catalytic triad of exo-inulinases [23][24][25]. In conclusion, our results suggest that the fungal mannitol pathway and exo-inulinase enzyme hold key roles for PEFA production in Rhodotorula strains.…”

“…The knowledge on the PEFA biosynthetic pathway and its components is limited. A recent study suggested that an exo-inulinase enzyme holds key roles in the PEFA production via a mannitol biosynthesis pathway using the polysaccharide inulin as the carbon source [ 23 ]. Hence, we used the recently identified protein sequence of exo-inulinase enzyme from R. paludigena P4R5 [ 23 ] to detect enzymes in the marine R. mucilaginosa 50-3-19/20B genome aided by BLAST suite [ 22 ].…”

“…A recent study suggested that an exo-inulinase enzyme holds key roles in the PEFA production via a mannitol biosynthesis pathway using the polysaccharide inulin as the carbon source [ 23 ]. Hence, we used the recently identified protein sequence of exo-inulinase enzyme from R. paludigena P4R5 [ 23 ] to detect enzymes in the marine R. mucilaginosa 50-3-19/20B genome aided by BLAST suite [ 22 ]. Herein, we report the existence of an exo-inulinase gene (as g1629.t1) and its genomic locus including its flanking genes deduced from the marine R. mucilaginosa 50-3-19/20B genome ( Table S2 ).…”

“…This result demonstrates that the exo-inulinase enzyme (g1629.t1) has orthologs in several fungi with annotation as either GH32 protein or β -fructofuranosidase ( Table S3 ). This putative exo-inulinase harbors known conserved motifs of exo-inulinases [ 23 , 24 , 25 ] as 189 FMNDPNGC 189 , 209 Q, 250 FS 251 , 315 RDP 317 , and 366 ECP 368 ( Figure 3 , marked by stars, numbering according to amino acid numbering of exo-inulinase enzyme of marine R. mucilaginosa ). Out of these residues, three amino acids 192 D- 316 D- 366 E form the conserved catalytic triad (marked by red stars in Figure 3 ) with 192 D serving as the nucleophile, 316 D as a stabiliser of the transient state and 366 E as the acid-base catalyst.…”

“…It also possesses a disordered region in the N-terminal region (1-159 residues). (B) Protein sequence alignment of exo-inulinase enzymes of marine R. mucilaginosa (g1629.t1) and R. paludigena strain P4R5 (Genbank: AZR37516.1,[23]) illustrating the presence of conserved motifs of exo-inulinases as 189 FMNDPNGC 189 ,209…”