Desempenho de Messastrum gracile (Chlorophyceae) submetida à diferentes ciclos de luz em meios de cultura comercial e alternativo
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Data
2022-02-25
Autores
Breda, Maria Julia Gonçalves
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Universidade Estadual Paulista (Unesp)
Resumo
Um dos fatores que dificulta a produção em larga escala de microalgas é o custo de energia e meio de cultura uma vez que, as microalgas necessitam de luz e nutrientes para seu crescimento. Este estudo visa avaliar se a redução do consumo de energia através do uso de diferentes ciclos de luz (claro/escuro) poderá manter elevada biomassa e valor nutricional destes microrganismos, podendo ser uma nova tecnologia adotada para a microalga Messastrum gracile (Reinsch) T. S. Garcia (CCMA-UFSCar 5). A microalga foi cultivada em dois meios de cultura, um comercial CHU12 e outro alternativo de extrato de macrófita (Eichhornia crassipes (Mait.) Solms (MART.) – ME) de acordo com os protocolos adotados. Além disso, para testar a variação dos efeitos dos ciclos de luz, quatro condições de luminosidades foram utilizadas: 24 h:0 h (luz constante); 20 h: 4 h; 16 h:8 h e 12 h:12 h (claro/escuro). Em termos de biomassa o custo da microalga no ciclo de luz 24 h: 0 h no 15° dia de crescimento apresentou o maior custo de produção por gramas (US$ 0.42), devido a elevada biomassa. Durante as horas de luz, a intensidade foi mantida em 60 μmolphoton m−2s−1. Na condição de luz constante (24 h:0 h) foi obtida a maior biomassa e tempo de duplicação, no entanto, em relação aos parâmetros como densidade celular média, carbono orgânico total, volume celular e comprimento total, os ciclos de luz 20 h:4 h e 16 h:8 h apresentaram maior desempenho. No ciclo 12 h:12 h o rendimento de M. gracile foi baixo. O meio de cultura de extrato de macrófita (ME) apresentou as maiores densidades do que o CHU12 nos ciclos de luz 24 h:0 h e 20 h:4 h. Somente no ciclo de luz 16 h:8 h a densidade celular foi maior no meio CHU12 a partir do 7° dia de crescimento. No ciclo de luz 12 h:12 h a densidade celular esteve abaixo de 35x105 cels mL-1 nos dois meios utilizados. Dentre os compostos nitrogenados a amônia foi a mais elevada, variando ao longo do período experimental. O ciclo de luz 24 h:0 h foi o que apresentou maior concentração de fósforo total. Assim, o meio de cultura apresentou influência direta na produção de M. gracile e os períodos escuros também influenciaram na biomassa da microalga. Em relação ao custo/benefício da produção de M. gracile nas condições de cultivo e ciclo de luz, o meio ME (24 h:0 h) apresentou o menor custo. Quanto maior a intensidade de luz consequentemente, ocorrerá maior biomassa. O meio CHU12 (comercial) contém todos os macro e micronutrientes adequados para o crescimento da microalga, no entanto, o uso de macrófita (Eichhornia crassipes) como meio de cultura é uma alternativa a ser adotada para esta microalga.
One of the features which hampers a large-scale microalgae production is the energy and culture medium cost, since the microalgae demands light ad nutrients for its growth. The present study aims to evaluate if the energy consumption reduction through the employment of distinct light cycles (light/dark) may keep elevated biomass and nutrient value for the microorganisms, which may present a new technology for microalgae Messastrum gracile (Reinsch) T. S. Garcia (CCMA- UFSCar 5). The microalgae were cultivated in two culture mediums: commercial CHU12 and an alternative based on macrophyte extract (Eichhornia crassipes (Mait.) Solms (MART.) – ME) according to adopted protocols. Besides, to evaluate the effects of light cycle variation, four light conditions were employed: 24 h:0 h (constant light); 20 h:4 h; 16 h:8 h and 12 h:12 h (light/dark). Regarding biomass, the microalgae cost with 24 h:0 h at growth day 15 presented higher production cost per grams (US$ 0.42), due to elevated biomass. During light periods, the light intensity was kept at 60 μmolphoton m− 2s− 1. At constant light condition (24 h:0 h) the highest biomass and duplication time were obtained, however, regarding average cell density, total organic carbon, cell volume and total length, the light cycles 20 h:4 h and 16 h:8 h presented better performance. In the 12 h:12 h cycle the M. gracile yield was low. The macrophyte extract culture medium (ME) presented better densities than CHU12 with 24 h:0 h and 20 h:4 h. Only in the 16 h:8 h cycle the cell density was higher in CHU12 medium from growth day 7. At 12 h:12 h cycle the cell density was below 35x105 cells mL-1 in both culture mediums. Among the nitrogenous compounds, the ammonia was the most elevated, varying along the experimental period. The 24 h:0 h cycle presented the highest total phosphorus concentration. Thus, the culture medium presented direct influence in the production of M. gracile and the dark periods also influenced in the microalgae biomass. Regarding cost-benefit, the ME medium (24 h:0 h) presented the lower cost. The higher the light intensity, consequently, the higher is the biomass. CHU12 medium contains all the suitable macro and micronutrients for the growth of the microalgae, however, the employment of the macrophyte (E. crassipes) as culture medium is an alternative to be adopted for this microalgae.
One of the features which hampers a large-scale microalgae production is the energy and culture medium cost, since the microalgae demands light ad nutrients for its growth. The present study aims to evaluate if the energy consumption reduction through the employment of distinct light cycles (light/dark) may keep elevated biomass and nutrient value for the microorganisms, which may present a new technology for microalgae Messastrum gracile (Reinsch) T. S. Garcia (CCMA- UFSCar 5). The microalgae were cultivated in two culture mediums: commercial CHU12 and an alternative based on macrophyte extract (Eichhornia crassipes (Mait.) Solms (MART.) – ME) according to adopted protocols. Besides, to evaluate the effects of light cycle variation, four light conditions were employed: 24 h:0 h (constant light); 20 h:4 h; 16 h:8 h and 12 h:12 h (light/dark). Regarding biomass, the microalgae cost with 24 h:0 h at growth day 15 presented higher production cost per grams (US$ 0.42), due to elevated biomass. During light periods, the light intensity was kept at 60 μmolphoton m− 2s− 1. At constant light condition (24 h:0 h) the highest biomass and duplication time were obtained, however, regarding average cell density, total organic carbon, cell volume and total length, the light cycles 20 h:4 h and 16 h:8 h presented better performance. In the 12 h:12 h cycle the M. gracile yield was low. The macrophyte extract culture medium (ME) presented better densities than CHU12 with 24 h:0 h and 20 h:4 h. Only in the 16 h:8 h cycle the cell density was higher in CHU12 medium from growth day 7. At 12 h:12 h cycle the cell density was below 35x105 cells mL-1 in both culture mediums. Among the nitrogenous compounds, the ammonia was the most elevated, varying along the experimental period. The 24 h:0 h cycle presented the highest total phosphorus concentration. Thus, the culture medium presented direct influence in the production of M. gracile and the dark periods also influenced in the microalgae biomass. Regarding cost-benefit, the ME medium (24 h:0 h) presented the lower cost. The higher the light intensity, consequently, the higher is the biomass. CHU12 medium contains all the suitable macro and micronutrients for the growth of the microalgae, however, the employment of the macrophyte (E. crassipes) as culture medium is an alternative to be adopted for this microalgae.
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Palavras-chave
Microalga, Microalgae, Macrófitas Aquáticas, Claro-escuro