Immobilisation of Solanum chrysotrichum plant cells within Ca-alginate gel beads to produce an antimycotic spirostanol saponin

Plant cell cultures of the Mexican species Solanum chrysotrichum can be established from friable calli. These cells produce an antifungal spirostanol saponin designated SC1. Plant cell immobilisation within Ca-alginate gel beads can lead to an enhancement in secondary metabolite production. Different matrices, obtained by varying calcium (0.1 to 0.8 mol.L(-1)) and alginate (1 to 1.5 % w/v) concentrations were used to study the influence of immobilisation parameters on the behaviour of S. chrysotrichum cells. Throughout the growth cycle and in the various immobilisation conditions, fresh and dry weight, SC1 yield and viability were measure. Important metabolic, morphological and physiological modulation seemed to be generated by the gel bead networks and by the cell-cell interactions inherent to the microenvironmental constraints. An accumulation of starch grains was observed through amyloplasts. Immobilised S. chrysotrichum cells accumulated 5 mg.g(-1) dry weight of SC1. Although this was four times less than the free cells, the desired metabolite was excreted into the surrounding medium (around 40% of the total production). (C) 2000 Editions scientifiques et medicales Elsevier SAS.