Sub-critical water technology for enhanced extraction of bioactive compounds from microalgae

Current extraction technologies, including chemical, mechanical, and biological based methods, routinely used to extract biochemical compounds from microalgal biomass are disadvantaged with lengthy processing steps, energy intensive operations, high operational cost, lower product yields and environmentally unfriendly processes. Hence, the search for a sustainable low-cost technology for high throughput extract ion of biochemicals from microalgal biomass is major research endeavour. Sub-critical 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 the factors that affect the production yield of bioactive compounds during SWE of microalgal biomass. The SWE process was investigated under different process conditions include temperature (180-374 ̊C), extraction time (1-20min) and biomass loading (5-40 wt%). The results showed that the highest carbohydrate and protein yields of 14.2 g/100g and 31.2 g/100g, respectively, were achieved at 277ºC, 5 min with 5% of biomass loading. This productivity level which is in keeping or higher than that of current production systems endorses SWE as a promising technique for extracting bioactive compounds from microalgae

Sub-critical water technology for enhanced extraction of carbohydrates and protein from chlorella vulgaris microalgae

Algae have many advantages such as fast growth rate, non-arable land requirement for grow and contain substantial amount of biochemical compounds such as lipid, carbohydrate and protein for value added products production. One of the new key alternatives is to extract microalgal biochemical by utilizing subcritical water extraction (SWE). This technique applies hot water under pressure sufficiently retains water in liquid state at temperature below the supercritical values. This study investigates the effectiveness of SWE to extract protein and carbohydrate from microalgae, Chlorella Vulgaris. The study was divided into three parts; (i) investigation of various parameters that affect the biochemical production (protein and carbohydrates), (ii) optimization of SWE and (iii) pre-treatment validation. Four different parameters include temperature (180-374 ˚C), time (1-20min), biomass loading (5-40 wt%) and particle size of biomass (38-250μm) were used to investigate on microalgal SWE. The SWE process was further optimized using central composite design (CCD). It was found that the highest protein and carbohydrate concentration of 31.16 g/100 g and 14.2 g/100gwere obtained at 5 wt.%microalgal biomass with 90 μm particulate size treated at 277°C for 5 min. The TOC yield of 8.01g/100g was obtained at 229ºC for 3min with 10wt.%microalgal biomass at 75μm particle size. Based on the statistical analysis, microalgae loading and extraction temperature have shown the most significant factors that affect the overall extraction of protein whereas extraction temperature were the significant factors for carbohydrate production. TOC yields were only affected by the microalgal loading of the microalgal biomass. This study was further investigated the effect of pre-treatment prior to microalgal SWE. The biomass was irradiated under sonication as the pre-treatment technique with different process parameters. The results concluded that the pre-treatment was not required as the results were comparable with SWE without pre-treatment hence it gives advantages in reducing the extraction costs and avoiding environmental problems (e.g. usage of solvents)

Subcritical water technology for enhanced extraction of biochemical compounds from Chlorella vulgaris

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