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Lactic acid is one of the backbone organic acids in Chinese baijiu. Its content affects both the fermentation process and the flavor and quality of baijiu. However, contribution of different microorganisms to lactic acid synthesis and the metabolism of lactic acid during strong-flavor baijiu fermentation have not yet been clarified. In this study, microbes and pathways involved in lactate synthesis during strong-flavor baijiu fermentation were revealed by RNA-seq. It was found that lactate was synthesized under microaerobic and anaerobic conditions, and both nitrogen and carbon metabolisms were involved. In the process of nitrogen metabolism, Acetobacter malorum, Acetobacter pasteurianus, Komagataeibacter xylinus, Pichia membranifaciensand Saccharomyces cerevisiaesynthesized d-lactate. Torulaspora delbrueckiisynthesized lactate through homolactic fermentation under microaerobic condition. In the process of strong-flavor baijiu fermentation, lactate is mainly synthesized by Lactobacillusthrough heterolactic fermentation. Lactobacillus ozensisand Lactobacillus diolivoranswere identified as two major lactate producers and they synthesized d-lactate under anaerobic condition. l-lactate could be synthesized by T. delbrueckii, L. ozensisand Lactobacillus acetotolerans. The results demonstrated a comprehensive and clarified mechanism of lactic acid synthesis during strong-flavor baijiu fermentation, and could provide a theoretical basis for regulation of lactic acid synthesis in the process of baijiu fermentation.

The thermolabile polymer substrate of flexible perovskite solar cells (f-PSCs) enables defect formation during solution treatment and annealing. This phenomenon is unamiable to the device’s efficiency and mechanical stability, which is the motivation of this work and drives the strategy regarding the multifunctional modification by introducing 7-amino-4-(trifluoromethyl)-2-benzopyrone (ATB) into the perovskite precursor solution. Results indicate that the ATB involvement contributes to the formation of high-quality perovskite films and passivates the defects in the perovskite film, extending the carrier lifetime and enabling a f-PSC with a power conversion efficiency (PCE) of 19.47%. The ATB participation also facilitates the bending stability of the flexible f-PSC device, where 89.1% of the initial PCE remains after 5000 bending cycles with a bending radius of 5 mm, compared to the 65.3% residual of the control device without ATB. Furthermore, the unencapsulated device exhibits an 82.8% remainder of the initial efficiency after 2100 h exposure at an ambient condition of 20 °C and 40 ± 5% relative humidity more excellent than the control (68.4%). Hopefully, this work presents a fresh strategy in enhancing the mechanical stability of flexible f-PSC device with a decent PCE.

The low-temperature preparation requirement of perovskite solar cells (PSCs) enables the fabrication of flexible perovskite solar cells (f-PSCs). This technique has great potential for commercialization but is still accompanied by challenges in preparing dense and low-defect perovskite films on flexible polymer substrates. In this work, propylammonium chloride (PACl) was introduced during the fabrication process of a two-step sequentially deposited perovskite film. This ammonium halide salt has a long alkyl chain that can be incorporated into the A sites lacking volatile cations in the perovskite lattice. Meanwhile, it can also induce the transformation of extended imperfections to a lower-dimensional perovskite material. By using PACl for interface treatment, 2D perovskite is formed on 3D perovskite, which passivates interface defects in perovskite thin films, inhibits ion migration at grain boundaries, and restrains hysteresis. By comparison, the n-i-p f-PSCs passivated by PACl have an exceptional power conversion efficiency (PCE) of 22.06%, an open-circuit voltage (VOC) of 1.19 V, and a fill factor (FF) of 79.02% without any deterioration in the short-circuit current density (JSC), which are superior to control device parameters (PCE─19.24%, VOC─1.11 V, and FF─76.09%). In addition, the PACl-passivated flexible device exhibited decent mechanical stability, where the stimulated PCE was maintained at 89% of the original value after 2000 cycles of bending tests with a bending radius of 5 mm.

The ever-increasing need for electricity in off-grid areas requires a safe and effective energy supply system. Considering the development of a sustainable energy system and the reduction of environmental pollution and energy cost per unit, this study focuses on the techno-economic study and optimal sizing of the solar, wind, bio-diesel generator, and energy storage structure. The emerging metaheuristic optimization method is used to estimate the techno-economic benefits of the suggested structure to provide the required electricity for a residential household. The optimal design is done with the harmony search (HS) method to validate the results obtained with the suggested algorithm. Minimizing the total annual cost (TAC) is a main objective for the design optimization of the system while satisfying the reliability and techno-enviro-economic constraints. The impact of the investment cost of biodiesel, biofuel cost, and reliability is investigated on the system sizing. The results show that the proposed algorithm has low simulation time (by 4.1 %) and the operating cost of the proposed algorithm is 1.12 % less than the existing HS algorithm based on the best TAC value. The TAC is received as $24,259 with the suggested method, which is the best optimal result compared to the result given by the HS algorithm. The proposed off-grid renewable energy system based on a bio-diesel generator is a viable and scalable solution to provide the required electricity for a residential household in all periods. The sensitivity analysis show that if the biofuel cost is reduced by 50.8 %, TAC will decrease by about 36.6 %. On the other hand, if the bio-diesel generator cost is reduced by 17 %, TAC will be decreased by 2.7 %. Finally, if the limit value of reliability is reduced from 2 to 0 %, TAC will increase by 13.2 %.