Producing carbohydrate-rich microalgal biomass grown under mixotrophic conditions as feedstock for biohydrogen production

Abstract

Available online xxxKeywords: Carbohydrate Biohydrogen Microalgae Chlorella Clostridium butyricum Dark fermentation a b s t r a c t Three indigenous microalgae strains (Scenedesmus subspicatus GY-16, Chlorella vulgaris FSP-E, and Anistrodesmus gracilis GY-09) were evaluated for their ability to accumulate carbohydrates to subsequently serve as feedstock for biohydrogen production. The results of photoautotrophic growth show that among the three strains examined, C. vulgaris FSP-E displayed the highest biomass productivity (825.6 mg/L/d) and carbohydrate productivity (365.8 mg/L/d). Mixotrophic growth of C. vulgaris FSP-E with the addition of 2.0 g/l of sodium acetate further increased the biomass and carbohydrate productivity to 1022.3 mg/L/d and 498.5 mg/L/d, respectively. Moreover, operating photobioreactor on semi-batch mode enhanced the stability for prolonged incubation of the carbohydrate-rich C. vulgaris FSP-E and the biomass and carbohydrate productivity obtained were 1063.3 and 384.8 mg/L/d, respectively.The biomass of C. vulgaris FSP-E was then used as feedstock for biohydrogen production via separate hydrolysis and fermentation processes. The acidic hydrolysate (hydrolyzed with 1% H 2 SO 4 ) was fermented with Clostridium butyricum CGS5, giving a maximum H 2 yield of 2.87 mmol H 2 /g biomass and a H 2 production rate of 176.9 ml/h / l, which are higher than most reported values. The results obtained in this work indicate that carbohydrate-based microalgae feedstock shows good potential for biohydrogen production.

Improving carbohydrate production of Chlorella sorokiniana NIES‐2168 through semi‐continuous process coupled with mixotrophic cultivation

“…Similar finding was reported by Nguyen et al [31], showing that the carbohydrate productivity of Chlamydomonas reinhardtii UTEX90 could reach 304 mg/L/day using fed-batch operation strategy. Thus, it clearly demonstrates that acetate could be a great inducer for both cell growth and carbohydrate synthesis, which is in agreement with previous reports [32]. After cultivation for three days, the consumption of acetate was much lower and excess acetate accumulation occurred because of the limited amount of nitrogen source, suggesting that acetate assimilation would be correlated to nitrate availability under mixotrophic fed-batch operation.…”

Enhancing Hydrogen Production from Chlorella sp. Biomass by Pre-Hydrolysis with Simultaneous Saccharification and Fermentation (PSSF)

“…It is clear that the processes used in the present study (SSF and PSSF) gave far higher HY compared to those reported earlier. Using SHF, the HY was in the range of 42-125 mL g-biomass −1 [17,24,66,67], obviously lower than that obtained in the present study under SSF (153 mL g-biomass −1 ) and PSSF (154.8 mL g-biomass −1 ). This was considered as due to the fact that the active enzymes present in the system continued to hydrolyze the biomass during SSF, producing additional reducing sugars for hydrogen production.…”

Long-term photosynthetic CO2 removal from biogas and flue-gas: Exploring the potential of closed photobioreactors for high-value biomass production

“…Prior operation, an abiotic CO /H 2 S removal test was performed in order to determine the optimum liquid to gas flow rates (L/G) ratio in the AC, which maximizes the CO 2 and H 2 S removal from biogas without compromising the CH 4…”

“…et al(2015). Microalgae identification was performed by microscopic observations (OLYMPUS IX70, USA) after sample fixation with 5% of lugol acid.The carbohydrate and protein content of the biomass was determined according to the methodology described inDubois et al (1956) andLowry et al (1951), respectively.For carbohydrates determination, 1.5 mL of cultivation broth (biomass concentration ~0.2 g L -1 ) was mixed with 4 mL of H 2 SO4 1 M. Afterwards, the sample was heated for 20 min at 100 ºC and centrifuged for 5 min at 10000 rpm. A volume of 0.5 mL of the supernatant was mixed with 0.5 mL of a 5% phenol solution and stood for 40 min.…”