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Open AccessArticle

The Use of Lignin as a Microbial Carrier in the Co-Digestion of Cheese and Wafer Waste

1
Institute of Food Technology of Plant Origin, Poznań University of Life Sciences, Wojska Polskiego 31, 60-637 Poznań, Poland
2
Department of General and Environmental Microbiology, Poznań University of Life Sciences, Wojska Polskiego 31, 60-637 Poznań, Poland
3
Institute of Biosystems Engineering, Poznań University of Life Sciences, Wojska Polskiego 50, 60-637 Poznań, Poland
*
Author to whom correspondence should be addressed.
Polymers 2019, 11(12), 2073; https://doi.org/10.3390/polym11122073
Received: 7 November 2019 / Revised: 3 December 2019 / Accepted: 7 December 2019 / Published: 12 December 2019
(This article belongs to the Special Issue Properties, Applications and Perspectives of Lignin)
The aim of the article was to present the effects of lignin grafted with polyvinylpyrrolidone (PVP) as a microbial carrier in anaerobic co-digestion (AcoD) of cheese (CE) and wafer waste (WF). Individual samples of waste cheese and wafers were also tested. The PVP modifier was used to improve the adhesive properties of the carrier surface. Lignin is a natural biopolymer which exhibits all the properties of a good carrier, including nontoxicity, biocompatibility, porosity, and thermal stability. Moreover, the analysis of the zeta potential of lignin and lignin combined with PVP showed their high electrokinetic stability within a wide pH range, that is, 4–11. The AcoD process was conducted under mesophilic conditions in a laboratory by means of anaerobic batch reactors. Monitoring with two standard parameters: pH and the VFA/TA ratio (volatile fatty acids-to-total alkalinity ratio) proved that the process was stable in all the samples tested. The high share of N–NH4+ in TKN (total Kjeldahl nitrogen), which exceeded 90% for WF+CE and CE at the last phases of the process, proved the effective conversion of nitrogen forms. The microbiological analyses showed that eubacteria proliferated intensively and the dehydrogenase activity increased in the samples containing the carrier, especially in the system with two co-substrates (WF+CE/lignin) and in the waste cheese sample (CE/lignin). The biogas production increased from 1102.00 m3 Mg−1 VS (volatile solids) to 1257.38 m3 Mg−1 VS in the WF+CE/lignin sample, and from 881.26 m3 Mg−1 VS to 989.65 m3 Mg−1 VS in the CE/lignin sample. The research results showed that the cell immobilization on lignin had very positive effect on the anaerobic digestion process. View Full-Text
Keywords: lignin; microbial carrier; cheese waste; wafer waste; biogas production lignin; microbial carrier; cheese waste; wafer waste; biogas production
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Pilarska, A.A.; Wolna-Maruwka, A.; Pilarski, K.; Janczak, D.; Przybył, K.; Gawrysiak-Witulska, M. The Use of Lignin as a Microbial Carrier in the Co-Digestion of Cheese and Wafer Waste. Polymers 2019, 11, 2073.

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