On anammox activity at low temperature: Effect of ladderane composition and process conditions

[Display omitted] •Cultivation temperature, anammox genera and ladderanes affect anammox performance.•Anammox activation energy (Ea) at 15–30 °C was 79 ± 18 kJ.mol−1.•Long-term cold exposure reduced Ea at 10–15 °C, not activity per se.•Marine “Ca. Scalindua” activity and Ea was exceptionally suitable for cold streams.•Ea improved with more C18 [3]-ladderanes over C20 and larger polar headgroup. The application of partial nitritation-anammox (PN/A) under mainstream conditions can enable substantial cost savings at wastewater treatment plants (WWTPs), but how process conditions and cell physiology affect anammox performance at psychrophilic temperatures below 15 °C remains poorly understood. We tested 14 anammox communities, including 8 from globally-installed PN/A processes, for (i) specific activity at 10–30 °C, (ii) composition of membrane lipids, and (iii) microbial community structure. We observed that membrane composition and cultivation temperature were closely related to the activity of anammox biomasses. The size of ladderane lipids and the content of bacteriohopanoids were key physiological components related to anammox performance at low temperatures. We also indicate that the adaptation of mesophilic cultures to psychrophilic regime necessitates months, but in some cases can take up to 5 years. Interestingly, biomass enriched in the marine genus “Candidatus Scalindua” displayed outstanding potential for nitrogen removal from cold streams. Collectively, our comprehensive study provides essential knowledge of cold adaptation mechanism, will enable more accurate modelling and suggests highly promising target anammox genera for inoculation and set-up of anammox reactors, in particular for mainstream WWTPs.