Table 1 Summary of recent studies employing enzymes for cell wall pretreatment
Microalgae species | Target product | Enzyme (with conditions) | Secondary and/or enhancing treatments | Yield/results/conclusions | References |
|---|---|---|---|---|---|
Chlamydomonas reinhardtii | Cell wall carbohydrates | 0.005% α-amylase, 90 °C, for liquefaction, and 0.2% glucoamylase, pH 4.5, 55 °C for saccharification | Yeast fermentation for ethanol production | 94% carbohydrate hydrolysis 29.2% ethanol production efficiency | Choi et al. (2010) |
Chlamydomonas reinhardtii | Native proteins and lipids | Gamete autolysin, pH 7.5, 23–37 °C; trypsin, pH 7.8, 37 °C | Organic solvent extraction | 85% cell lysis and 55% total protein release with gamete autolysin and 73% total lipid release with trypsin | Soto Sierra et al. (2017) |
Chlorella sp. | Cell wall carbohydrates | Cellulases, xylanases, and amylases enzymes, pH 4.8, 50 °C | Cells chilled with 95% (v/v) ethanol, cold dried, and ground prior to enzymatic application | 2.9–5.0% hydrolyzed glucose depending on species and 4.8–8.6 total reducing sugars | Rodrigues and da Silva Bon (2011) |
Chlorella vulgaris | Lipids | Cellulase (Celluclast 1.5 L) β-glucosidases (Novozyme 188), pH 4.8, 50 °C | Organic solvent extraction | 85.3% cell wall hydrolysis after 72 h Improved lipid extraction yield (1.29- to 1.73-fold) depending on solvent utilized | Cho et al. (2013) |
Chlorella vulgaris | Cell wall carbohydrates | Alcalase®, pH 8.0, 50 °C | Aerobic digestion for methane production | Enhanced methane production (64% increase in yield) | Mahdy et al. (2014b) |
Chlorella vulgaris | Lipids | Snailase (37 °C), lysozyme (55 °C), cellulose (55 °C), no pH specified | Organic solvent extraction | 7% lipids extracted with snailase, 22% lipids extracted with lysozyme, 24% lipids extracted with cellulose | Zheng et al. (2011) |
Chlorella vulgaris, Scenedesmus dimorphus, and Nannochloropsis sp. | Cell wall and lipids | Cellulase, snailase, neutral protease, alkaline protease, and trypsin, pH 4.0, no temperature specified | Ultrasonication | 49.82% lipid recovery in C. vulgaris, 46.81% lipid recovery in S. dimorphus, 11.73% lipid recovery in Nannochloropsis sp. | Liang et al. (2012) |
Haematococcus pluvialis | Carotenoids | Glucanex®, pH 4.5, 55 °C | Ultrasonication | 83.9% carotenoid extraction | Machado et al. (2016) |
Haematococcus pluvialis | Astaxanthin | 0.1% Protease K and 0.5% Driselase®, pH 5.8, 30 °C | Organic solvent extraction | Low total carotenoid yield after enzymatic treatment | Mendes-Pinto et al. (2001) |
Nannochloropsis sp. | Lipids | Feedlyve® GMA (Fe-GMA)-galactomannanase and Cellulyve® 50LC (Ce-50LC)-β-cellobiosidase/β-glucosidase, pH 6.0, 45 °C | Organic solvent extraction | 68.6% lipid extraction | Zuorro et al. (2015) |
Nannochloropsis sp. | Lipids | Ternary mixture of one cellulose and two hemicellulases, pH 5.0, 50 °C | Organic solvent extraction | 37.2 g lipids per 100 g of dry biomass recovered | Zuorro et al. (2016) |