ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Microbiotechnology
This article is part of the Research TopicAdvances in Anaerobic Microbiology: Insights from 13th International Symposium on Anaerobic Microbiology (ISAM2025)View all 5 articles
Augmentation of psychrophilic anaerobic digestion with psychrotolerant Serratia marcescens, and calcium phosphate (CaHPO4·2H2O) and hematite (α-Fe2O3) nano-additives
Provisionally accepted
Haripriya Rama1,2*
Busiswa Ndaba3
Mokhotjwa Simon Dhlamini2
Malik Maaza4,5
Nicolene Cochrane6
Ashira Roopnarain1,7- 1Microbiology and Environmental Biotechnology Research Group, Agricultural Research Council – Natural Resources and Engineering, Pretoria, South Africa
- 2Department of Physics, University of South Africa - Florida Campus, Johannesburg, South Africa
- 3Institute for Catalysis and Energy Solutions, University of South Africa - Florida Campus, Johannesburg, South Africa
- 4Nanosciences African Network Materials Research Department, iThemba Laboratory for Accelerator Based Sciences, Somerset West, South Africa
- 5UNESCO UNISA Africa Chair in Nanosciences & Nanotechnology, Pretoria, South Africa
- 6AGRIMETRICS, Agricultural Research Council, Pretoria, South Africa
- 7Department of Environmental Sciences, University of South Africa - Florida Campus, Johannesburg, South Africa
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Psychrophilic anaerobic digestion (PAD) requires optimization to improve methane production at low temperatures (<20 °C). This study aimed to improve methane production via bioaugmentation with psychrotolerant Serratia marcescens (SM) and biostimulation with nano-additives, comprising calcium phosphate (CaP) and hematite (α-Fe2O3) nanoparticles (NPs), during batch PAD of cattle manure and food waste at 15 °C. The highest methane yields were obtained from treatment with SM and both NPs (163.9 ± 18.0 mL CH4 g-1 VS), thereafter with the combination of CaP and α-Fe2O3 NPs (143.9 ± 50.2 mL CH4 g-1 VS). The lowest yield was observed in the control (70.2 ± 4.9 mL CH4 g-1 VS) followed by treatment with SM alone (124.6 ± 20.3 mL CH4 g-1 VS). Treatment with CaP and α-Fe2O3 NPs reduced the lag phase more than the other treatments. Moreover, the addition of nano-additives biostimulated PAD without significantly altering the microbial community composition. The dominant genera included Bacteroides, Acinetobacter, and Methanosarcina (a mixotrophic methanogen) after batch PAD across all treatments. This research provides new insights on the augmentative effect of SM, CaP and α-Fe2O3 NPs on methane production and microbial community dynamics during PAD.
Keywords: anaerobic digestion, bioaugmentation, biostimulation, Low temperature, microbial communities, Sclerocarya birrea, Serratia marcescens
Received: 02 Feb 2026; Accepted: 06 Feb 2026.
Copyright: © 2026 Rama, Ndaba, Dhlamini, Maaza, Cochrane and Roopnarain. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Haripriya Rama
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