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Feedstock variability represents a challenge in lignocellulosic biorefineries, as it can influence both lignocellulose deconstruction and microbial conversion processes for biofuels and biochemicals production. The impact of feedstock variability on microbial performance remains underexplored, and predictive tools for microbial behaviour are needed to mitigate risks in biorefinery scale‐up. Here, twelve batches of corn stover were deconstructed via deacetylation, mechanical refining, and enzymatic hydrolysis to generate lignin‐rich and sugar streams. These batches and their derived streams were characterised to identify their chemical components, and the streams were used as substrates for producing muconate and butyrate by engineered Pseudomonas putida and wildtype Clostridium tyrobutyricum, respectively. Bacterial performance (growth, product titers, yields, and productivities) differed among the batches, but no strong correlations were identified between feedstock composition and performance. To provide metabolic insights into the origin of these differences, we evaluated the effect of twenty‐three isolated chemical components on these microbes, including three components in relevant bioprocess settings in bioreactors, and we found that growth‐inhibitory concentrations were outside the ranges observed in the streams. Overall, this study generates a foundational dataset on P. putida and C. tyrobutyricum performance to enable future predictive models and underscores their resilience in effectively converting fluctuating lignocellulose‐derived streams into bioproducts. [ABSTRACT FROM AUTHOR]

The rate and yield of B-side quinone reduction in Rhodobacter capsulatus reaction centers was determined. It was found that the rate of the ground state charge-recombination reaction in the YFH RC is faster than the rate for ground state charge-recombination reaction in the native RC, whereas the competitive rate constants on the A-side of wild type RC effectively suppress the ground state electron process and B-side electron transfer occurs with a yield of ~45% in the YHF mutant RC.

Subpicosecond transient absorption studies are reported for a set of Rhodobacter (R.) capsulatus bacterial photosynthesis reaction centers (RCs) designed to probe the origins of the unidirectionality of charge separation through one of two electron transport chains in the native pigment-protein complex. The result states an upper limit of V(sub L)(super 2)/V(sub M)(super 2) less than or equal to 4 for the contribution of the electronic coupling elements to the relative rates of electron transfer to the L versus M sides of the wild-type RC.

Material design issues are considered by evaluating the stability, organization, and photophysics of bacterial photosynthetic reaction centers (RCs) encapsulated in thermoresponsive, soft nanostructures. The dynamics of the electron-transfer in the warm and cold phase of the RCs are presented.

The substitution of phenylalanine [Phe(L181)] by tyrosine(Tyr) and Tyr(M 208) by Phe amino acid in the reaction centers (RCs) of Rhodobacter capsulatus yields an RC with 15 percent yield of charge separation to the B-side bacteriophephytin (H(sub B)). The analysis is based on the relative bleaching of the quinone (Q(sub x)) bands of H(sub A) and H(sub B) at 542 and 527 nm, respectively.

The rates of Forster-Dexter excitation transfer between two chromophores involved in photosynthesis were investigated. In addition, the extent to which approximations to Forster-Dexter transfer agree with detailed balance results and the implications of the result for multichromophore systems were examined. The question of whether there is a consistent definition of a characteristic energy for each excited chromophore such that a Boltzmann factor for the ratio of uphill to downhill pairwise rates exists was also addressed.

Comparative studies of excited bacteriochlorophyll (Bchl) decay in the membrane-bound core antenna of wild-type and mutant reaction center strains of Rhodobacter capsulatus revealed that the shortest-lived component is insensitive to mutation in contrast to the longer-lived components which are sensitive to mutation. Furthermore, the increasing amplitudes and lifetimes of the longer-lived components determine the increasing trend of the light-harvesting factor 1 (LH1*) average lifetime.

Using electron spin polarized paramagnetic resonance (ESP EPR) spectroscopy, an investigation was made on the effect of the rate of primary charge separation, metal-site occupancy, and H-subunit content on the observed P865+QsubAsup- charge-separated state. Fe-removed and Zn-substituted reaction centers from Rhodopseudomonas sphaeroides R-26 were utilized to observe specific electron transfer rates (kQ) from the intermediate acceptor H- to the primary acceptor QA. Correlation of the transient EPR and optical results showed that the slow KQ rate in Fe-removed RCs was not dependent on the occupancy of the H-subunit or Fe-site.

Femtosecond transient absorbance spectroscopy was used to study the primary electron transfer in single reaction center crystals from Rhodobacter sphaeroides. The findings have shown the ability to resolve ultrafast photosynthetic function in single crystals and allow ultrafast function to be directly correlated with structure.

Direct excitation of the bacteriochlorophyll dimer (P) induced electron transfer to the B-side bacteriochlorophytin yields 30% of P(sup)+H(sub)B and decays with a time constant of 1.5-3 nanoseconds when the secondary quinone Q(sub)B site is occupied.

Results show that the B-side electron-transfer pathway can create a productive, long-lived charge separation spanning the membrane during quinone reduction in mutant bacterial reaction centers. Data indicate that P(sup)+Q(sub)B(sup)-states are distinct, whereasP(sup)+Q(sub)B(sup)- formed by the B side do not decay via the pathway utilizing A-side cofactors.