Comparison of different machine learning algorithms to estimate liquid level for bioreactor management

Estimating the liquid level in an anaerobic digester can be disturbed by its closedness, bubbles and scum formation, and the inhomogeneity of the digestate. In our previous study, a soft-sensor approach using seven pressure meters has been proposed as an alternative for real-time liquid level estimation. Here, machine learning techniques were used to improve the estimation accuracy and optimize the number of sensors required in this approach. Four algorithms, multiple linear regression (MLR), artificial neural network (ANN), random forest (RF), and support vector machine (SVM) with radial basis function kernel were compared for this purpose. All models outperformed the cubic model developed in the previous study, among which the ANN and RF models performed the best. Variable importance analysis suggested that the pressure readings from the top (in the headspace) were the most significant, while the other pressure meters showed varying significance levels depending on the model type. The sensor that experienced both headspace and liquid phases depending on the level variation incurred a higher error than other sensors. The results showed that the ML techniques can provide an effective tool to estimate digester liquid levels by optimizing the number of sensors and reducing the error rate

유용미생물을 활용한 아조염료의 생분해 및 전사체 분석을 통한 분해경로 탐색

The goal of this study was to select the most appropriate microbial consortium for efficient bioremediation of azo dye wastewater. A consortium composed of two bacterial cultures (Mesorhizobium sp. and Sphingomonas melonis) and two yeast cultures (Apiotrichum mycotoxinivarans and Meyerozyma guilliermondi) achieved more than 80% decolorization within 24 h (50 and 100 mg/L dye). The chemical oxygen demand (COD) removal rate for the bacterial consortium (B-C) reached 97% in 72 h while the yeast consortium (Y-C) and the total microbial consortium (T-C; bacterial and yeast consortia combined) achieved 98.0% and 97.5%, respectively, in 24 h, indicating potential mineralization of the azo dye Acid Blue 113. Moreover, there was a positive relationship between cell growth and the azo dye degradation rate in all consortia. The Fourier transform infrared (FT-IR) spectra profiles for yeast-containing consortia showed a rapid disappearance of absorbance at the azo bond specific wavenumber (1455 cm-1) (24 h), while the B-C showed disappearance within 72 h. Metabolic products containing -NH2 groups were also detected based on the absorbance at the 1300 cm-1 wavenumber, reflecting an occurrence of azo bond cleavage. It was concluded that the data for decolorization, COD removal, cell growth, and FT-IR spectra collectively provide evidence for azo dye decolorization and potential mineralization of the dye by the bacterial and yeast consortium. Moreover, transcriptomic analysis using RNA-sequencing further explained the potential mechanisms of azo dye biodegradation by Sphingomonas melonis. NAD(P)-dependent oxidoreductase and type 1 glutamine amidotransferase were differentially expressed in the dye treatment, indicating that degradations of the azo bond and the aromatic compounds could be catalyzed by these enzymes. The selected microbial consortia could be applied for the bioremediation of azo dye wastewater at the industrial scale of varying environmental conditions.|이 연구의 목적은 아조 염료 폐수의 효율적인 생물학적 분해를 위한 가장 적절한 미생물 컨소시엄을 선택하는 것이다. 2 종의 박테리아(Mesorhizobium sp. 및 Sphingomonas melonis)와 2 종의 효모(Apiotrichum mycotoxinivarans 및 Meyerozyma guilliermondi)로 구성된 컨소시엄은 24 시간만에 50 또는 100 mg/L의 azo 염료(Acid Bule 113)를 80 % 이상 탈색을 달성했습니다. 화학적 산소 요구량 (COD) 제거율은 24 시간 후 효모 컨소시엄 (Y-C)과 총 미생물 컨소시엄 (T-C, 박테리아 및 효모 컨소시엄 결합)이 각각 98.0 %와 97.5 %를 달성하는 반면, 박테리아 컨소시엄 (B-C)은 72 시간 후 97 % 달성하였다. 또한, 모든 컨소시엄에서 세포 성장과 azo 염료 분해율은 비례관계를 가지고 있다. Fourier transform infrared (FT-IR) 스펙트럼 분석 결과, Y-C는 아조 결합을 나타내는 특정 주파수 (1455 cm-1)에서 24 시간 후 흡광도의 급격한 감소를 보인 반면, BC는 72 시간 후 소멸을 보였다. 또한, 아조 결합의 절단을 의미하는 –NH2 그룹의 주파수 (1300 cm-1)에서도 azo 염료가 분해되는 시간에 따라서 검출되었다. 탈색 실험, COD 제거, 세포 성장 및 FT-IR 스펙트럼에 대한 결과를 종합해보면, 박테리아 및 효모 컨소시엄이 의한 아조 염료의 잠재적인 무기화 작용에 대한 증거를 제공한다고 평가되었다. 또한, RNA 시퀀싱을 통한 전사체 분석은 Sphingomonas melonis의 잠재적 아조 염료 분해 매커니즘을 밝혀내었다. 즉, NAD(P)-dependent oxidoreductase 및 type 1 glutamine amidotransferase는 염색물질의 처리구에 차별적으로 많이 발현된 것으로 보아, 이러한 효소가 염색물질의 아조결합구조 및 그 분해산물인 방향족화합물의 분해에 관여한 것으로 판단되었다. 선발 된 미생물 컨소시엄은 다양한 환경적 요인에 노출되어 있는 산업규모의 아조 염료 폐수 처리에 생물학적처리를 위해 적용될 수 있을 것으로 보인다.Chapter 1. Introduction 1 Chapter 2. Literature Review 4 2.1 Principles of color chemistry 4 2.2 Azo dye decolorization and degradation 5 2.2.1 Azo dye treatment 5 2.2.2 Biological treatment of azo dyes 6 2.2.3 Enzymatic decolorization and degradation of azo dyes 6 2.3 RNA sequencing for transcriptomic analysis 11 Chapter 3. Materials and methods 12 3.1 Isolation of efficient microorganisms for azo dye biodegradation and their identification 12 3.2 Experimental culture setup for biodegradation of the azo dye Acid Blue 113 15 3.3 UV-vis spectrophotometric analysis for cell growth and dye biodegradation 16 3.4 Monitoring of azo dye biodegradation based on FT-IR analysis 17 3.5 Monitoring of the fate of organic compounds (azo dye and glucose) based on COD analysis 17 3.6. RNA isolation and sequencing procedure for RNA-seq analysis for the dye degradation 18 Chapter 4. Results and discussion 19 4.1 Dye decolorization by various cultures 19 4.2 Monitoring of organics through COD analysis 22 4.3 Comparison of cultural growth and concomitant decolorization activity in the microbial consortia 24 4.4 FT-IR and GC-MS analyses of the biodegradation process by microbial consortia for the azo dye AB113 26 4.5 Implications of the synergistic effects of inter genus co-culture in terms of bioremediation of azo dyes 29 4.6. Transcriptomic analysis of degradation of Acid Blue 113 30 Chapter 5. Conclusion 35 References 37 Academic achievement 49Maste

Long-term effectiveness of bioaugmentation with rumen culture in continuous anaerobic digestion of food and vegetable wastes under feed composition fluctuations

Biogas plants treating food waste (FW) often experience feed load and composition fluctuations. In Korea, vegetable waste from the preparation of kimchi comprises over 20% of the total FW production during the Kimjang season. The large production of Kimjang waste (KW) can cause mechanical and operational problems in FW digesters. This study investigated the long-term effectiveness of bioaugmentation with rumen culture (38 months) in an anaerobic reactor co-digesting FW with varying amounts of KW. The bioaugmented reactor maintained better and stabler performance under recurrent fluctuations in feed characteristics than a nonbioaugmented control reactor, particularly under high ammonia conditions. Bioaugmentation increased microbial diversity, thereby improving the resilience of the microbial community. Some augmented microorganisms, especially Methanosarcina, likely played an important role in it. The results suggest that the proposed bioaugmentation strategy may provide a means to effectively treat and valorize KW-and potentially other seasonal lignocellulosic wastes-by co-digestion with FW

Effects of Different pH Control Strategies on Microalgae Cultivation and Nutrient Removal from Anaerobic Digestion Effluent

This study investigated nutrient removal from anaerobic digestion effluent by cultivating mixed-culture microalgae enriched from anaerobic sludge under different pH conditions: RUC (uncontrolled), R7???8 (maintained at 7???8), and R<8 (maintained below 8). Significant amounts of NH4+-N were lost by volatilization in RUC cultures due to increased pH values (???8.6) during the early period of cultivation. The pH control strategies significantly affected the biological NH4+-N removal (highest in R7???8), microalgal growth (highest in R7???8), biomass settleability (highest in R<8), and microalgal growth relative to bacteria (highest in R<8) in the cultures. Parachlorella completely dominated the microalgal communities in the inoculum and all of the cultures, and grew well at highly acidic pH (<3) induced by culture acidification with microalgal growth. Microalgae-associated bacterial community structure developed very differently among the cultures. The findings call for more attention to the influence and control of pH changes during cultivation in microalgal treatment of anaerobic digestion effluent

Complex network analysis of slaughterhouse waste anaerobic digestion: From failure to success of long-term operation

The study explored slaughterhouse waste (SHW) as prime feedstock associated with and without supplement of an external slowly degradable lignocellulosic carbon source to overcome the synergistic co-inhibitions of ammonia and fatty acids. Long-term solid-state digestion (SSD) and liquid-state digestion (LSD) were investi-gated using a mixture of pork liver and fat. At 2.0 g volatile solids (VS) L-1 d-1 of organic loading rate (OLR), the two reactors of SSD experienced operational instability due to ammonia inhibition and volatile fatty acid (VFA) accumulation while LSD successfully produced 0.725 CH4 L CH4 g- 1VS during 197 d of working days under unfavorable condition with high total ammonia nitrogen (> 4.7 g/L) and VFAs concentration (> 1.9 g/L). The network analysis between complex microflora and operational parameters provided an insight for sustainable biogas production using SHW. Among all, hydrogenotrophic methanogens have shown better resistance than acetoclastic methanogens

Tracking microbial community shifts during recovery process in overloaded anaerobic digesters under biological and non-biological supplementation strategies

Anaerobic digestion encounters operational instability due to fluctuations in organic loading. Propionic acid (HPr) is frequently accumulated due to its unfavorable reaction thermodynamics. Here, 'specific' bioaugmentation using HPr enrichment cultures (three different injection regimes of quantity and frequency) was compared with 'non-specific' bioaugmentation using anaerobic sludge, and with non-biological supplementation of magnetite or coenzyme M. The specific bioaugmentation treatments showed superior recovery responses during continuous feeding after a peak overload. A 'one-shot' bioaugmentation with enrichment showed the best remediation, with similar to 25% recovery time and >10% CH4 conversion efficiency compared to the control. Consecutive bioaugmentation showed evidence of increased stability of the introduced community. Families Synergistaceae, Syntrophobacteraceae, and Kosmotogaceae were likely responsible for HPr-oxidation, in potential syntrophy with Methanoculleus and Methanobacterium. The different supplementation strategies can be considered to reduce the effect of start-up or overload in anaerobic digesters based on the availability of supplementation resources.11Nsciescopu