Decreased enzyme activities, ammonification rate and ammonifiers contribute to higher nitrogen retention in hyperthermophilic pretreatment composting

Keystone Genes Confer Superior Performance in Hyperthermophilic Composting

“…The enriched amyA gene might catalyze starch degradation to release more monomeric or oligomeric sugars in hyperthermic conditions [38,39], which could enhance heat production by microbial metabolism and facilitate humic substance formation by the Maillard reaction (condensation between amides and reducing sugars) [40]. All N-cycling genes exhibited lower relative abundance in the hTC treatment, suggesting a shift to hinder some microbial functional groups that can utilize N-containing substrates or losses in certain organisms that thrive at elevated composting temperatures [9,[41][42][43]. These results were in accordance with our nding that the relative abundance of the genus Bacillus, a strongly ammonifying taxon [44], was lower in hTC (Additional le 1, Figure S7).…”

“…For example, the high temperatures at which thermostable C-degrading enzymes in hyperthermophiles can operate at allow more substrate to dissolve, which can increase diffusion and mass transfer rates and thus shift the equilibrium [39,48]. Additionally, although a wide variety of hyperthermophiles catalyze exergonic redox reactions involving nitrogenous compounds, nitri cation, denitri cation and dissimilatory nitrate reduction were strongly inhibited at high temperatures during composting [9,42,49]. The correlations between the microbial community composition (Bray-Curtis distance) and functional structure were further con rmed by Procrustes tests (for hTC, P < 0.05, M 2 = 0.8026, R = 0.3111, 9999 permutations; for cTC, P < 0.01, M 2 = 0.70544, R = 0.5428, 9999 permutations; Additional le 1, Figure S8) and pairwise similarity with linear regressions (P < 0.001, similarity was calculated by Bray-Curtis distance, Additional le 1, Figure S9).…”

“…The nished product, which looks like soil, is high in carbon (C) and nitrogen (N) and is an excellent medium for growing plants [5,8]. However, conventional thermophilic composting (cTC) technology still suffers from low composting temperatures, high nitrous oxide (N 2 O) emissions and unsatisfactory germination indices (GIs), leading to a reduction in the environmental bene ts of composting plants [2,9,10]. Given that microorganisms play a crucial role in all events related to the biotransformation of organic substrates during composting [11], hyperthermophilic microorganisms have been recently adopted in composting ecosystem known as hyperthermophilic composting (hTC) [12][13][14].…”

Physicochemical and microbiological dynamics in composting of organic waste using a new bioreactor model

“…Even the beginning of the bio-oxidative phase presenting high temperatures (>50°C), thermotolerant mesophilic microorganisms are able to withstand this treatment [63]. Even when there is no change in the total plate count of microorganisms, there may be a reduction in diversity indices, which may favor certain microbial groups [64].…”

“…In composts without the addition of starter cultures, several changes naturally occur in the physical and chemical structure, because the microorganisms present are capable of biological activity to increase the temperature (55-70°C), which provides the dominance of thermophilic microorganisms with high degradability of organic matter [45]. Thus, the endogenous populations of microorganisms adapt to environmental variations provided by the composting process and plays an important role in the degradation of organic matter, mineralization of nutrients, control of pathogens, and stabilization of the compost [45,64].…”