The purple phototrophic bacteria (PPB) are photosynthetic microorganisms that degrade the organic carbon and nutrients under anaerobic conditions by using light as an energy source. Light intensity and temperature are considered as substantial factors for the PPB growth. However, few studies addressed their impacts on mixed PPB culture. This research was carried out to evaluate the growth of mixed PPB using batch photobioreactors in an irradiation apparatus under different (i) light intensities of 10, 20, 40, and 60 W/m^2 and (ii) temperatures of 30, and 25°C. Experimental data were processed using Logistic, Monod-like function, and Aiba models. The obtained growth kinetic parameters showed that mixed PPB growth is highly affected by temperature and light intensity. The specific growth rate (k_C) evaluated by the Logistic model increased by increasing light intensity until peaking at 0.379〖 h〗^(-1) under 40 W/m^2 and 30 °C, then it dropped. Monod-like function and Aiba models were used for determining number of parameters including; the maximum specific growth rate (μ_max) that increased by increasing light intensity till it peaked at 0.390〖 h〗^(-1) for the Monod-Like model, and 0.981 h^(-1) for Aiba model at light intensity of 40 W/m^2 and temperature of 30 °C, then it dropped. The half saturation light constant (I_K or K_I) reached highest value of 90 W/m^2 with the Monod-like (I_K) and 85 W/m^2 with the Aiba (K_I) at light intensity of 60 W/m^2 and temperature of 25 °C. Estimated half saturation coefficient for the substrate (K_S) was 50 mgCOD/L , and the biomass yield (Y) ranged between (0.5- 1) mg VSS/mg COD. Whereas the photoinhibition effect 〖(K〗_i) was described only by Aiba model, the lowest estimated value was 38.349 W/m^2 at light irradiation of 40 W/m^2 and temperature of 30 °C. Decreasing temperature to 25 °C resulted in significantly decrease of μ_max, and increase of light constants included K_i, I_K, and K_I. Thus, light intensity of 40 W/m^2 and temperature of 30 °C were the best conditions for mixed PPB growth.
I batteri fototrofici viola (PPB) sono microrganismi fotosintetici che degradano il carbonio organico e i nutrienti in condizioni anaerobiche utilizzando la luce come fonte di energia. Tuttavia, pochi studi hanno affrontato il loro impatto sulla cultura mista PPB. Questa ricerca è stata condotta per valutare la crescita mista di PPB utilizzando fotobioreattori batch in un apparato di irradiazione a diverse (i) intensità di luce, pari a 10, 20, 40, e 60 W/m^2, e (ii) temperature, pari a 30 e 25 °C. I dati sperimentali sono stati elaborati utilizzando i modelli Logistic, Monod-like e Aiba. I parametri cinetici di crescita ottenuti hanno mostrato che la crescita mista di PPB è fortemente influenzata dalla temperatura e dall'intensità della luce. Il tasso di crescita specifico (k_C) valutato dal modello logistico è aumentato al crescere dell'intensità della luce fino a raggiungere un picco di 0.379h^(-1) sotto 40 W/m^2 e 30 °C, dopodiché è diminuito. La funzione simile a Monod e i modelli Aiba sono stati utilizzati per determinare il numero di parametri tra cui: il tasso di crescita specifico massimo (μ_max), che è aumentato al crescere dell'intensità della luce fino a raggiungere il picco di 0.390h^(-1) per il modello Monod-Like e 0.981h^(-1) per il modello Aiba, con un'intensità luminosa di 40 W/m^2 e temperatura di 30 °C, per poi diminuire. La costante di luce di mezza saturazione (I_K o K_I) ha raggiunto il valore massimo di 90 W/m^2 con Monod-like (I_K ) e 85 W/m^2 con Aiba (K_I) a un'intensità luminosa di 60 W/m^2 e temperatura di 25 °C. Il coefficiente di semisaturazione stimato per il substrato (K_S) è risultato pari a 50 mgCOD/L, e la resa in biomassa (Y) è variata tra (0.5-1) mg VSS/mg COD.h. L'effetto di fotoinibizione (K_i) è stato descritto soltanto dal modello Aiba, e il valore più basso stimato è stato di 38.349 W/m^2 con un'irradiazione luminosa di 40 W/m^2 e una temperatura di 30 °C. La diminuzione della temperatura a 25 ° C ha comportato una diminuzione significativa di μ_max, e l'aumento delle costanti di luce K_i,I_K e K_I. Pertanto, un'intensità luminosa di 40 W/m^2 e una temperatura di 30 °C sono risultate le condizioni migliori per la crescita mista di PPB.
The effect of light intensity and temperature on the growth of mixed purple phototrophic bacteria
Abusil, Omima Musa Mohmed
2021/2022
Abstract
The purple phototrophic bacteria (PPB) are photosynthetic microorganisms that degrade the organic carbon and nutrients under anaerobic conditions by using light as an energy source. Light intensity and temperature are considered as substantial factors for the PPB growth. However, few studies addressed their impacts on mixed PPB culture. This research was carried out to evaluate the growth of mixed PPB using batch photobioreactors in an irradiation apparatus under different (i) light intensities of 10, 20, 40, and 60 W/m^2 and (ii) temperatures of 30, and 25°C. Experimental data were processed using Logistic, Monod-like function, and Aiba models. The obtained growth kinetic parameters showed that mixed PPB growth is highly affected by temperature and light intensity. The specific growth rate (k_C) evaluated by the Logistic model increased by increasing light intensity until peaking at 0.379〖 h〗^(-1) under 40 W/m^2 and 30 °C, then it dropped. Monod-like function and Aiba models were used for determining number of parameters including; the maximum specific growth rate (μ_max) that increased by increasing light intensity till it peaked at 0.390〖 h〗^(-1) for the Monod-Like model, and 0.981 h^(-1) for Aiba model at light intensity of 40 W/m^2 and temperature of 30 °C, then it dropped. The half saturation light constant (I_K or K_I) reached highest value of 90 W/m^2 with the Monod-like (I_K) and 85 W/m^2 with the Aiba (K_I) at light intensity of 60 W/m^2 and temperature of 25 °C. Estimated half saturation coefficient for the substrate (K_S) was 50 mgCOD/L , and the biomass yield (Y) ranged between (0.5- 1) mg VSS/mg COD. Whereas the photoinhibition effect 〖(K〗_i) was described only by Aiba model, the lowest estimated value was 38.349 W/m^2 at light irradiation of 40 W/m^2 and temperature of 30 °C. Decreasing temperature to 25 °C resulted in significantly decrease of μ_max, and increase of light constants included K_i, I_K, and K_I. Thus, light intensity of 40 W/m^2 and temperature of 30 °C were the best conditions for mixed PPB growth.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/195589