Subcritical Water Technology for Enhanced Extraction of Biochemical Compounds fromChlorella vulgaris

Abstract

Subcritical water extraction (SWE) technology has been used for the extraction of active compounds from different biomass materials with low process cost, mild operating conditions, short process times, and environmental sustainability. With the limited application of the technology to microalgal biomass, this work investigates parametrically the potential of subcritical water for high-yield extraction of biochemicals such as carbohydrates and proteins from microalgal biomass. The SWE process was optimized using central composite design (CCD) under varying process conditions of temperature (180–374°C), extraction time (1–20 min), biomass particulate size (38–250 μm), and microalgal biomass loading (5–40 wt.%). Chlorella vulgaris used in this study shows high volatile matter (83.5 wt.%) and carbon content (47.11 wt.%), giving advantage as a feedstock for biofuel production. The results showed maximum total carbohydrate content and protein yields of 14.2 g/100 g and 31.2 g/100 g, respectively, achieved under the process conditions of 277°C, 5% of microalgal biomass loading, and 5 min extraction time. Statistical analysis revealed that, of all the parameters investigated, temperature is the most critical during SWE of microalgal biomass for protein and carbohydrate production.

Study on the Effect of Reaction Temperature, Time, and Solid Loading on Lignin from Oil Palm Frond (OPF) under Subcritical Phenol Conditions as a Precursor for Carbon Fiber Production

“…Several studies have reported that the effect of biomass loading is less significant when compared to temperature and reaction time 33) 34) . Awaluddin et al (2016) 35) have shown similar trends in their study.…”

Green Extraction of Bioactive Compounds from Microalgae

“…The main parameters that affect the extraction yield and the composition of the extract in SWE are the temperature, the extraction time, the biomass loading and the particle size. Some of the works that apply SWE for the extraction of microalgal carbohydrates evaluate the effect of these extraction parameters [34,35]. The results of these studies showed that the polysaccharide content on the final extract is greatly affected by the temperature.…”

“…However, at higher temperature, the carbohydrate extraction yield decreases due to the degradation of the polysaccharides and besides, to the lower contribution of the reduction effect of the subcritical water dielectric constant. Apart from high temperatures, Awaluddin et al showed that long extraction times and high biomass loading negatively affected the carbohydrate recovery [35]. In other studies, the effect of SWE conditions was also evaluated in terms of chemical composition and bioactivity of the obtained extracts.…”

Scenedesmus obliquusmicroalga‐based biorefinery – from brewery effluent to bioactive compounds, biofuels and biofertilizers – aiming at a circular bioeconomy

“…It was determined that a temperature of 175 °C is adequate for extraction of phenols from Chlorella sp., while a longer extraction time does not have a favorable impact on the content of phenols in extracts. Moreover, in a study performed by Awaluddin et al . in which proteins and carbohydrates were extracted from C. vulgaris , the authors concluded that higher temperatures (above 160 °C) are needed for efficient extraction.…”