Pseudozyma aphidis DSM 70725 was found to be a novel producer of mannosylerythritol lipids (MELs). The MELs were quantified by HPLC. Glucose as carbon source for precultivation supported growth well. By contrast, at concentrations >30 g l(-1) in preculture, subsequent MEL formation in the main culture with soybean oil as sole carbon source was reduced. The type of substrate supply considerably influenced MEL formation. High concentrations of soybean oil (80 ml l(-1)) at init favored the production process when compared to a stepwise (20 ml l(-1)) addition. Mannose or erythritol were suitable second carbon sources that enhanced the MEL yield with soybean oil as preferred primary substrate. After 10 days, a maximum yield of 75 g l(-1) was attained during shake-flask cultivation. Biofuel (rapeseed oil methyl ester) also resulted in high yields of MEL, but glucose reduced the MEL yield. Analysis by GC-MS showed that all fatty acids contained in MEL and derived from soybean oil or related methyl ester were degraded by C2-units to differing extents. The surface (water/air) and interfacial (water/hexadecane) tension of the MELs produced from different carbon sources were reduced to a minimum of 26.2 mN m(-1) and 1 mN m(-1), respectively.

Two strains of Pseudozyma aphidis, DSM 70725 and DSM 14930, were used for the bioreactor production of mannosylerythritol lipids (MELs). Foam formation interfered substantially with the cultivation process. Soybean oil was simultaneously employed as both carbon source and anti-foam agent. Primary MEL formation occurred after nitrate limitation. After a first short time-period of nitrate limitation and further nitrate addition, MELs were secreted in spite of nitrate excess. The sedimentation of MEL-enriched beads indicated enhanced product formation. Maximum yield, productivity and yield coefficient of 165 g l(-1), 13.9 g l(-1) day(-1) and 0.92 g g(-1) were achieved using strain DSM 14930 with additional substrate-feeding (glucose, sodium nitrate, yeast extract) and a foam-controlled soybean oil supply.

SUMMARY In vitamin D deficient rats the influence of diphenylhydantoin (DPH) and phénobarbital (PB) pretreatment on intestinal uptake of 45calcium and on the activity of CaBP was studied. The DPH rats show in contrast to the PB and control rats a significantly reduced intestinal uptake of 45calcium. However, the activity of CaBP was similar in all investigated groups. These results suggest a possibly special effect of DPH on the development of the calcium and bone disorders that have been observed in patients treated with anticonvulsant drugs. RÉSUMÉ On a étudié chez des rats qui manquaient de vitamine D, l'effet d'un pré‐traitement avec de la diphénylhydantoïne (DPH) et du phénobarbital (PB) sur l'absorption intestinale de calcium 45 et sur l'activité du CaPB. Les rats qui avaient du DPH, en opposition aux rats de contrôle et aux rats avec PB, avaient une absorption intestinale de calcium 45 significativement réduite. L'activité du CaPB était cependant semblable chez tous les groupes. Ces résultats suggèrent un effet possible particulier de la DPH sur l'origine des troubles du calcium et du métabolisme des os, qui ont été observés chez des patients en traitement avec des produits anticonvulsivants.

Downstream processing of mannosylerythritol lipids produced by Pseudozyma aphidisPseudozyma aphidis DSM 14930 was used for the bioreactor production of mannosylerythritol lipids (MEL). A scheme is presented for the isolation and purification of MEL by using different solvents. Adsorption experiments of MEL at Amberlite XAD resins were performed. Up to 93% (wt-%) MEL could be transferred from the culture suspension into a newly formed, highly viscous solid phase by heating the culture suspension to !100 7C. This phase contained on average 87% (wt-%) MEL and could be simply isolated by pouring off the supernatant, without producing solvent waste.

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