The enhancement of energy supply in syngas-fermenting microorganisms.

After the second industrial revolution, social productivity developed rapidly, and the use of fossil fuels such as coal, oil, and natural gas increased greatly in industrial production. The burning of these fossil fuels releases large amounts of greenhouse gases such as CO2, which has caused greenhouse effects and global warming. This has endangered the planet's ecological balance and brought many species, including animals and plants, to the brink of extinction. Thus, it is crucial to address this problem urgently. One potential solution is the use of syngas fermentation with microbial cell factories. This process can produce chemicals beneficial to humans, such as ethanol as a fuel while consuming large quantities of harmful gases, CO and CO2. However, syngas-fermenting microorganisms often face a metabolic energy deficit, resulting in slow cell growth, metabolic disorders, and low product yields. This problem limits the large-scale industrial application of engineered microorganisms. Therefore, it is imperative to address the energy barriers of these microorganisms. This paper provides an overview of the current research progress in addressing energy barriers in bacteria, including the efficient capture of external energy and the regulation of internal energy metabolic flow. Capturing external energy involves summarizing studies on overexpressing natural photosystems and constructing semiartificial photosynthesis systems using photocatalysts. The regulation of internal energy metabolic flows involves two parts: regulating enzymes and metabolic pathways. Finally, the article discusses current challenges and future perspectives, with a focus on achieving both sustainability and profitability in an economical and energy-efficient manner. These advancements can provide a necessary force for the large-scale industrial application of syngas fermentation microbial cell factories.

An integrated laboratory experiment for the determination of main components in different food samples.

An integrated laboratory experiment was designed for introducing biochemistry students to basic static biochemistry to deepen their understanding on the properties and analysis of biomolecules such as total carbohydrates, lipid, protein, and protein-constituent amino acids. Food represents a very important source of biomolecules of technological and functional interest; therefore, 15 types of food samples were selected to demonstrate the analysis of basic composition of these biomolecules. In this experiment, students learnt testing the total carbohydrates of all the food samples using 3,5-dinitrosalicylic acid (DNS) method, while performing acid hydrolysis. Then, lipid extraction was done using Soxhlet extraction method in order to determine the crude lipid concentration in different samples. After this, the students learnt testing crude protein content of these samples by using Kjeldahl method, and amino acid analysis was performed using HPLC. From the experiments, students grasped the concept and advantages of these methods and deepened their understanding on compositional analysis of different food samples. This laboratory exercise can be included into any college-level biochemistry courses and gives hands-on experience to the students for conducting scientific research in the field of life sciences, food science, and other bio-related fields.

Functions of bacteria and archaea participating in the bioconversion of organic waste for methane production.

Anaerobic digestion (AD) is a widely applied technology for treating organic wastes to generate renewable energy in the form of biogas. The effectiveness of AD process depends on many factors, among which the most important is the presence of active and healthy microbial community in the anaerobic digesters, which needs to be explored. However, the deciphering of microbial populations and their functions during the AD process of different materials is still incomplete, which restricts the understanding of its long-term performance under different operational conditions. This review describes the type, morphology, functions, and specific growth conditions of commonly found hydrolytic, acidogenic, acetogenic bacteria, and archaea during the AD process. The effects of microbes on the performance and stability of the digestion process are also presented. Furthermore, the article offers a deep understanding of the AD management strategies for the enhancement of methane production and the efficiency of the energy conversion process of various organic wastes.

Optimizing key factors for biomethane production from KOH-pretreated switchgrass by response surface methodology.

Anaerobic digestion (AD) is one of the best technologies for producing methane from biomass wastes with limited environmental impacts. Most AD plants need a continuous and stable supply of feedstock for their sustained operation for which lignocellulosic biomass can be effectively utilized. Switchgrass (SG), also known as Panicum virgatum, is a tall-growing grass which exists throughout the year in areas with warm climate and has the potential to produce biomethane. The present work investigated anaerobic digestion performance of SG while focusing on enhancing the methane yield by employing central composite design of response surface methodology (RSM). The aim of this research was to find out the best level of factors including feed-to-inoculum (F/I) ratio, organic loading (OL), and pH for optimizing the desired output of biomethane production from 3% KOH-pretreated SG. Results revealed that the highest value of experimental methane yield was 288.4 mL/gVS at the optimal F/I ratio, pH, and OL of 1, 6.96, and 24 gVS/L, respectively. Moreover, 3% KOH pretreatment improved the biodegradability of SG significantly from 14.23 to 85.53%. This study forms the basis for future application of SG for enhanced methane production.

Enhancement of methane production from Cotton Stalk using different pretreatment techniques.

China produces large amount of cotton stalk (CS) residues as agricultural biomass, which are incinerated on-site, causing air pollution. The high organic content of CS could be utilized for biogas production, but the direct digestion without pretreatment always leads to a low methane yield and biodegradability, due to the complicated structure of lignocellulose. In order to search best fitting pretreatment methods in effective anaerobic digestion (AD) of CS, effects of various pretreatments including KOH, NaOH, Ca(OH)2, alkali hydrogen peroxide (AHP), H2SO4, H3PO4 and steam explosion (SE) were studied. It was seen that all treatments resulted in varying methane yields. Among all the pretreatments, acid pretreatment is not suitable for AD of CS. The results showed that the highest cumulative methane yield (CMY) of 192.4 mL·gVS-1 was obtained after 3% AHP pretreatment of CS, and the methane yield improved by 254.3% than the untreated CS. Therefore, AHP treatment was proven to be an efficient pretreatment technique. XRD and FTIR analyses had shown that pretreated CS had favorable structural changes. This research is beneficial in developing environment friendly and cost-effective pretreatment technologies to utilize CS for methane production in future application.

Employing response surface methodology (RSM) to improve methane production from cotton stalk.

China is the largest cotton producer with the cotton output accounting for 25% of the total world's cotton production. A large quantity of cotton stalk (CS) waste is generated which is burned and causes environmental and ecological problems. This study investigated the anaerobic digestibility of CS by focusing on improving the methane yield by applying central composite design of response surface methodology (RSM). The purpose of this study was to determine the best level of factors to optimize the desired output of methane production from CS. Thus, it was necessary to describe the relationship of many individual variables with one or more response values for the effective utilization of CS. The influences of feed to inoculum (F/I) ratio and organic loading (OL) on methane production were investigated. Results showed that the experimental methane yield (EMY) and volatile solid (VS) removal were calculated to be 70.22 mL/gVS and 14.33% at F/I ratio of 0.79 and organic loading of 25.61 gVS/L, respectively. Characteristics of final effluent showed that the anaerobic system was stable. This research laid a foundation for future application of CS to alleviate the problems of waste pollution and energy output.

Pretreatment methods of lignocellulosic biomass for anaerobic digestion.

Agricultural residues, such as lignocellulosic materials (LM), are the most attractive renewable bioenergy sources and are abundantly found in nature. Anaerobic digestion has been extensively studied for the effective utilization of LM for biogas production. Experimental investigation of physiochemical changes that occur during pretreatment is needed for developing mechanistic and effective models that can be employed for the rational design of pretreatment processes. Various-cutting edge pretreatment technologies (physical, chemical and biological) are being tested on the pilot scale. These different pretreatment methods are widely described in this paper, among them, microaerobic pretreatment (MP) has gained attention as a potential pretreatment method for the degradation of LM, which just requires a limited amount of oxygen (or air) supplied directly during the pretreatment step. MP involves microbial communities under mild conditions (temperature and pressure), uses fewer enzymes and less energy for methane production, and is probably the most promising and environmentally friendly technique in the long run. Moreover, it is technically and economically feasible to use microorganisms instead of expensive chemicals, biological enzymes or mechanical equipment. The information provided in this paper, will endow readers with the background knowledge necessary for finding a promising solution to methane production.