A study was carried out to select the conditions for cultivation of Kluyveromyces marxianus CDBBL 278 in solid-state culture (SSC) using polyurethane foam (PUF) as an inert support. PUF was impregnated with culture media containing lactose (50 g/L) as the carbon and energy source. Evaluation of culture parameters during different growth phases was carried out by respirometry. The effect of inoculum level, buffer capacity of the medium, and nitrogen source upon the yield of biomass on lactose (Yx/s) and production of lactase and inulinase was investigated. The highest lactase titre was achieved with an inoculum level of 1 x 10(7) cells per gram of wet matter (gwm) and 20% of the total nitrogen source provided as urea. The best biomass yield (0.37) was obtained when less than 40% of the total nitrogen was provided as urea. Using potassium phosphate allowed 90% substrate consumption in 30 h. In the best conditions, intracellular lactase and extracellular inulinase activities of 1147.7 IU/gX and 241.6 IU/gX were obtained, respectively, with a lag phase of 13.8 h and a rate of respiratory activity (microCO2) of 0.23 +/- 0.01 h(-1). To our knowledge, this is the first report on lactase production by K. marxianus CDBBL 278 in SSC. This study gives basic information about biomass yield and enzyme production using lactose as the sole carbon source in SSC on an inert support.
Invertase from Aspergillus niger C28B25 was produced by solid-state fermentation (SSF), and fermented solids were used directly as a biocatalyst for batch and continuous hydrolysis of sucrose in a packed-bed reactor under different operational conditions with varied temperature, sucrose concentration and feed flow rate. The SSF allowed obtaining a biocatalyst with an invertase activity of 82.2 U/g db. The biocatalyst maintained its activity in the range of 40 to 70ºC for at least 70 h of continuous operation. The highest hydrolysis rate (12.3 mg/U h) was obtained at 70ºC with 2M sucrose under batch conditions. Continuous hydrolysis in 20-mL and 200-mL bioreactors at 60ºC led to sucrose hydrolysis above 60% (8.5 residence times) and above 55% (4.5 residence times), respectively. The auto-immobilised biocatalyst produced by SSF without recovery, purification and immobilisation stages offers an economical alternative for the development of accessible biocatalysts that can be applied in batch or continuous sucrose hydrolysis processes. This study shows the potential of biocatalyst production by SSF for other enzymatic systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.