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| Author(s): |
Ana Lucia Morocho Jacome
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2014-08-07 |
| Examining board members: |
Joao Carlos Monteiro de Carvalho;
José Gregorio Cabrera Gomez;
Viviane Maimoni Gonçalves;
Mauri Sergio Alves Palma;
Celia Leite Sant'Anna
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| Advisor: | Joao Carlos Monteiro de Carvalho |
| Abstract | |
Arthrospira (Spirulina) platensis have compounds of interest in the food, pharmaceutical and cosmetic industries. Industrial production involves high volumes of water and its viability should contemplate medium reuse, aiming to reduce not only nutrient costs, but also environmental pollution, thus becoming a sustainable process. This work had as main objective the evaluation of A. platensis culture medium reuse through the physicochemical treatments flocculation and adsorption. Thus, this cyanobacterium was cultivated in tubular photobioreactor (PBR) by fed-batch and continuous processes at light intensity 120 µmol photons m-2 s-1 under pH control. Treatment techniques were developed for culture medium from fed-batch process to properly removal of organic matter (OM) and pigments (60 - 96 %), thus allowing its reuse in new cultures. A. platensis was cultivated in treated medium using Erlenmeyer flasks, with the evaluation of parameters such as maximum cell concentration (Xm), chlorophyll content (Chl) and protein content in dry biomass (PTN). For simultaneous flocculation and adsorption with powdered activated carbon (PAC), two flocculants were used: ferric chloride (F) and ferric sulfate (S), as well as different contact times. In the simultaneous process of F flocculation and PAC adsorption, optimum conditions were: PAC = 24.4 mg L-1 and F = 20.3 mg L-1 for 30.4 min contact time; results were: Xm = 4893 ± 33 mg L-1, Chl = 24.3 ± 0.1 mg g-1, PTN = 36.1 ± 0.6 %. Optimal conditions in the simultaneous process of S flocculation and PAC adsorption were: PAC = 40.0 mg L-1 and S = 32.8 mg L-1 for 36.1 min contact time; results were: Xm = 4863 ± 64 mg L-1, Chl = 24.5 ± 0.6 mg g-1, PTN = 60.1 ± 0.6 %. In the sequential process of F flocculation followed by adsorption with granular activated carbon (GAC), optimal conditions were reached at GAC = 108.4 g and F = 10.0 mg L-1 for 30.8 min of residence time, at which Xm = 3140 ± 77 mg L-1, Chl = 35.4 ± 0.2 mg g-1 and PTNPTN = 44.9 ± 0.0 % were obtained. Moreover, medium treated at each optimal condition were also tested in tubular PBRs, reaching values of Xm, Chl and PTN higher than those obtained with standard medium. Furthermore, the simultaneous process of cell cultivation in tubular PBR and continuous adsorption of spent cultivation medium through GAC column removed 51 - 79 % of OM and pigments. It was showed that 75 % of treated medium in the feed medium does not cause significant decrease in cell productivity (PX) and results were: steady-state cell concentration (Xs) = 1568 ± 15 mg L-1, PX = 941 mg L-1 d-1, PTN = 42.0 ± 0.6 %, with 65 % reduction in medium price. At last, it can be inferred that the use of physicochemical processes in medium treatment is feasible for reuse in A. platensis cultivation, including that in tubular PBR, leading to considerable increase in chlorophyll and protein contents of the biomass obtained with treated medium. (AU) | |