Salem Rana, Soliman Moomen, Fergala Ahmed, Audette Gerald F, ElDyasti Ahmed
Civil Engineering Department, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada.
Department of Biotechnology, Delft University of Technology, Mekelweg 5, 2628 CD Delft, The Netherlands.
Polymers (Basel). 2021 May 14;13(10):1579. doi: 10.3390/polym13101579.
With the adverse environmental ramifications of the use of petroleum-based plastic outweighing the challenges facing the industrialization of bioplastics, polyhydroxyalkanoate (PHA) biopolymer has gained broad interest in recent years. Thus, an efficient approach for maximizing polyhydroxybutyrate (PHB) polymer production in methanotrophic bacteria has been developed using the methane gas produced in the anaerobic digestion process in wastewater treatment plants (WWTPS) as a carbon substrate and an electron donor. A comparison study was conducted between two experimental setups using two different recycling strategies, namely new and conventional setups. The former setup aims to recycle PHB producers into the system after the PHB accumulation phase, while the latter recycles the biomass back into the system after the exponential phase of growth or the growth phase. The goal of this study was to compare both setups in terms of PHB production and other operational parameters such as growth rate, methane uptake rate, and biomass yield using two different nitrogen sources, namely nitrate and ammonia. The newly proposed setup is aimed at stimulating PHB accumulating type II methanotroph growth whilst enabling other PHB accumulators to grow simultaneously. The success of the proposed method was confirmed as it achieved highest recorded PHB accumulation percentages for a mixed culture community in both ammonia- and nitrate-enriched media of 59.4% and 54.3%, respectively, compared to 37.8% and 9.1% for the conventional setup. Finally, the sequencing of microbial samples showed a significant increase in the abundance of type II methanotrophs along with other PHB producers, confirming the success of the newly proposed technique in screening for PHB producers and achieving higher PHB accumulation.
由于使用石油基塑料对环境的负面影响超过了生物塑料工业化所面临的挑战，聚羟基脂肪酸酯（PHA）生物聚合物近年来受到了广泛关注。因此，一种利用废水处理厂（WWTPS）厌氧消化过程中产生的甲烷气体作为碳底物和电子供体，在甲烷营养型细菌中最大化聚羟基丁酸酯（PHB）聚合物产量的有效方法已经被开发出来。使用两种不同的回收策略，即新设置和传统设置，在两个实验装置之间进行了比较研究。前一种设置旨在在PHB积累阶段之后将PHB生产者循环回系统中，而后一种设置则在生长的指数阶段或生长阶段之后将生物质循环回系统中。本研究的目的是使用两种不同的氮源，即硝酸盐和氨，在PHB产量以及其他操作参数（如生长速率、甲烷吸收速率和生物质产量）方面比较这两种设置。新提出的设置旨在刺激积累PHB的II型甲烷营养菌生长，同时使其他PHB积累菌能够同时生长。所提出方法的成功得到了证实，因为在富含氨和硝酸盐的培养基中，混合培养群落的PHB积累百分比分别达到了59.4%和54.3%，这是有记录以来的最高值，而传统设置的这两个百分比分别为37.8%和9.1%。最后，微生物样本的测序显示II型甲烷营养菌以及其他PHB生产者的丰度显著增加，证实了新提出的技术在筛选PHB生产者和实现更高PHB积累方面的成功。
