Table 2 Biotechnological modifications of microalgae for enhanced biofuel production

C. reinhardtii

Nuclear transformation; Heterologous expression; CRISPRi-based transcriptional silencing; CRISPR–Cas9-based target-specific knockout; Overexpression; Gene knockout

Acetyl-CoA synthetase (ACS2); Acyl-ACP thioesterase (DtTE); Phosphoenolpyruvate carboxylase (PEPC1); Phospholipase A2 (PLA2); Phosphorus stress response 1 (PSR1); DNA-binding-with-one-finger (Dof, crDOF)

Neutral lipid, total lipid, FA content and lipid productivity increased

[185, 193,194,195,196,197,198,199]

C. sorokiniana

Overexpression and transcriptomics

Carbonic anhydrase (CA); rbcL and accD

Lipid productivity increased

[200, 201]

Mortierella alpina

Construction and overexpression CCMP1545 (MpFADS6)

Delta-6 desaturase (FADS6)

Eicosapentaenoic acid (EPA) content increased

[202]

N. oceanica

Overexpression and knockdown

Malonyl CoA-acylcarrier protein transacylase (MCAT); Type-1 diacylglycerol acyltransferase (NoDGAT1A); Type-2 diacylglycerol acyltransferases (DGAT2); Fatty acid desaturases (FAD); bZIP1 transcription factor (NobZIP1)

Neutral lipid, SFA, MUFA, PUFA and EPA content increased

[186, 203,204,205,206,207,208]

N. salina

Overexpression of transcription factor; Heterologous expression

Basic helix–loop–helix (NsbHLH2); Basic leucine zipper transcription factors (NsbZIP1); AP2 type TF Wrinkled1 (NsAtWRI1)

Total lipid and FA content increased

[209,210,211]

P. tricornutum

Overexpression

Glucose-6-phosphate dehydrogenase (G6PD); Malic enzyme (PtME); Glycerol-3-phosphate acyltransferase (GPAT1); Lysophosphatidic acid acyltransferase (LPAT1)

Total lipid and neutral lipid content and productivity increased

[212,213,214]

S. obliquus

Overexpression

Type-2 diacylglycerol acyltransferse (DGTT1)

Total lipid content and productivity increased

[215]

Schizochytrium sp.

Overexpression

Malonyl-CoA: ACP transacylase (MAT); Malic enzyme; Codon-optimized ELO3 gene

Total lipid, PUFA and Docosahexaenoic acid content increased

[216, 217]