Table 1 Initial evaluation of the medium components’ potentials for the optimization of lipid productivity

CaCl₂

Versatile effector in plant cells; reported to be essential for induction of lipid synthesis

[50–52]

Yes

FeSO₄

Influence on growth and lipid metabolism reported

[51, 53–55]

Yes

H₂SO₄

Sulfur supply ensured by sulfate anions from diverse other medium components; nevertheless varied as provided together with FeSO₄ in one stock solution

Yes^b

K₂HPO₄/KH₂PO₄

Essential phosphorus source (nucleic acid synthesis)

[54]

Yes

KOH

Potassium excess by phosphate salts; nevertheless varied as provided together with Na₂EDTA in one stock solution

Yes^c

MES

Trade-off between osmotic inhibition and buffer capacity; alkaline pH may inhibit cell cycle

[56]

Yes

MgSO₄

Influence on growth and lipid production reported; effector of acetyl-CoA carboxylase, an essential enzyme during lipid biosynthesis; central atom of chlorophyll

[51, 57, 58]

Yes

NaCl

Reported to increase lipid production; excess may cause metabolic burden (ATP dependent sodium exporters) and thus inhibit growth

[59, 60]

Yes

Na₂EDTA

Commonly used metal chelator; excess may cause growth repression due to ion depletion

[51, 55]

Yes

NaNO₃

Essential nitrogen source (protein synthesis)

[54]

Yes

Penicillin-G

Support of long-time sterile conditions; not metabolized (data not shown)

No

Trace elements (CoSO₄, CuSO₄, H₃BO₃, MnCl₂, Na₂MoO₄, ZnSO₄)

Numerous studies about wastewater detoxification available, but only limited information concerning metabolism and lipid production; general pattern: little amounts essential, but high level cytotoxic (e.g., inhibition of photosynthesis); thus clustered to one input variable

[61–66]

Yes^a