Consideraciones físicas y geométricas acerca del crecimiento de Pichia pastoris en tiras de espuma de poliuretano

Abstract

This work introduces the use of polyurethane foam (PUF) slabs for solid-substrate fermentation. Attention is paid to the distribution and properties of the liquid broth within the slabs in relation to the growth parameters of Pichia pastoris. The experimental setup was made of thin slabs supported horizontally by screens within cylindrical chambers. This way, water loss due to compression or gravity drain was minimal and exposure to tangential air flow was maximal. The highest biomass was Xmax = 39.5±3.3 gL-1 with (So) of 150 gL-1 of glucose. Biomass yield, Yx/s followed the correlation, Yx/s = 0.525-0.0018S0 (R2 = 0.996), and the growth rate m = 0.24 h-1/(S0/34.6). The respiratory quotient, RQ, followed a biphasic pattern with a maximal RQ » 1 when S0 = 50 gL-1. PUF micrographs showed that liquid was not retained when the integrity of the polyurethane network was disrupted at cutting edges of the slabs with an approximate depth of 0.025 cm, but the fraction of disrupted PUF would be small for wide slabs and h = 0.7 cm. The use of horizontal PUF slabs with thickness of 0.7 cm seems to be a practical way to upscale solid state fermentation (SSF) since a squared meter of this material could produce 83 g of yeast.