bioreactor bacteria diversity
The main objective of the study was to determine the effect of different dosages of NaOH alkali pretreatment on the lignocellulosic structures and the methane production of crops residues. In this regard, NaOH pretreatment was implemented with different dosages on three different crops residues, wheat, rye, and rice straws. Substrates were soaked into NaOH solutions at different dosages with solid to liquid ratios of 100 and 200 gTS/L to investigate both conditions. The anaerobic digestion process was conducted using AMPTSII under mesophilic conditions. By 8% NaOH pretreatment dosage, the reduction of hemicellulose and lignin was 81% and 62% for rice straw, 86% and 69% for wheat straw, 80% and 74% for rye straw, respectively. The concentrations of CODs in the liquid fraction after pretreatment were regarded as 3 times higher than in untreated samples. Pretreatment with 8% NaOH dosage increased the methane yield of rice, wheat, and rye straws by 55%, 40%, and 46% respectively. Samples from digesters that produced the highest methane yield were chosen for further molecular analysis. Compared to untreated digesters, 16S rRNA gene amplicon sequencing revealed more diverse microbial communities in NaOH pretreated digesters.