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Abstract: We studied the production of surfactin by Bacillus pumilus UFPEDA 448 in solid-state fermentation (SSF), using a medium based on okara with the addition of sugarcane bagasse as a bulking agent. The optimum proportions of okara and sugarcane bagasse were 50% each, by mass. Due to the relatively high production of proteases during SSF, pre-hydrolysis of the okara with a protease did not improve surfactin levels. The optimum temperature for surfactin production was 37°C, with the incubation temperature affecting the ratios of the various surfactin homologues produced. Cultivation in column bioreactors with forced aeration under optimized conditions gave a surfactin level of 809mgL−1 of impregnating solution, which corresponds to 3.3gkg-dry-solids−1. This is the highest surfactin level that has been produced to date in SSF with a non-recombinant microorganism. The peak O2 uptake rate was 20mmolmin−1 kg-initial-dry-solids−1, corresponding to metabolic waste heat production rate of 182Wkg-initial-dry-solids−1. The tensioactive properties of the surfactin were similar to those reported in the literature for surfactin produced by submerged fermentation. These results suggest that it might be feasible to use SSF to produce surfactin but at large scale special attention will need to be given to heat removal. [Copyright &y& Elsevier]

Solid-state fermentation can be used to produce pectinases using agro-industrial byproducts. However, heat and mass transfer limitations make it difficult to control the temperature within the bioreactor, especially at large scale, so reliable scale-up strategies are essential. In the current work, we scaled up the production of pectinases in packed-bed bioreactors, from 12 g to 30 kg of dry substrate, the biggest scale yet reported for pectinase production. When compaction occurred, bed temperatures up to 47 °C were recorded and the pectinase activity in different regions of the bed at 26 h varied from 11 to 28 × 10 3 U kg −1 . When compaction was avoided, the maximum bed temperature was 32 °C and the pectinase activity at 26 h varied from 17 to 20 × 10 3 U kg −1 . The best result was obtained with a 40-cm high bed containing 27 kg of wheat bran and 3 kg of sugarcane bagasse, with switching of the temperature of the saturated inlet air between 24 °C and 32 °C. Under these conditions, the maximum productivity was 1840 U kg −1 h −1 at 10 h. We propose that the process can be scaled up to production scale by maintaining the same bed height and operational strategy, while increasing the width of the bed to several meters. If the superficial velocity of the air is maintained constant at 0.1 m s −1 , then the performance at scales involving several tonnes of solid substrate should be similar to that obtained in pilot-scale bioreactor in the current study. [ABSTRACT FROM AUTHOR]