Background/Objectives: The effects of thermal drying on the viability of beneficial microorganisms immobilized in biochar, as well as on biochar nutrient retention, remain insufficiently understood. This study aimed to evaluate how drying temperature influences the survival of hyper-ammonia-producing bacteria (HAB) immobilized on pine wood biochar and to assess the impact of subsequent storage on bacterial recovery and nutrient stability. Methods: Biochar was inoculated with HAB and subjected to drying at temperatures ranging from 40 to 60 °C. Following drying, samples were characterized and stored for 30 days. Microbial revival was assessed through reculturing, while changes in surface functional groups were analyzed using FTIR spectroscopy. Nutrient retention, particularly nitrogen content, was also evaluated. Results: Higher drying temperatures resulted in reduced immediate microbial revival during reculturing. However, samples exhibiting limited immediate recovery demonstrated enhanced revival after the 30-day storage period. FTIR analysis revealed that drying temperature modified the availability of surface functional groups associated with microbial attachment and activity. Nutrient analysis indicated only minor reductions in nitrogen retention in biochar dried at temperatures above 55 °C. Conclusions: Drying temperature significantly affects both the short-term survival and post-storage recovery of beneficial microorganisms immobilized in biochar. While elevated temperatures may initially suppress microbial activity, recovery potential during storage remains substantial. Optimizing drying conditions is therefore essential to balance microbial viability with nutrient retention in biochar-based formulations.

The many uses of biochar extend to microbial enhancement in fermentation processes because it acts as a catalyst and a support medium. This study explores how varying biochar properties specifically concentration, temperature, and particle size affect the growth of hyper-ammonia-producing bacteria (HAB), using commercially sourced pine wood-derived biochar. Fermentation experiments were conducted using enriched rumen fluid under controlled conditions to monitor bacterial growth via optical density (OD600) over a 48-hour period. Our results showed that microbial proliferation was significantly influenced by all three parameters. The optimal growth was observed at 0.15% biochar concentration, a temperature of 45°C, and a particle size of 250 µm. While lower concentrations and smaller particles promoted microbial adhesion and colonization, higher levels appeared to hinder growth, likely due to surface saturation and reduced pore accessibility. SEM imaging supported these findings by revealing structural changes on the biochar surface at different concentrations, highlighting its role in microbial distribution. Regression analysis confirmed a strong correlation between biochar parameters and microbial activity, although no single variable stood out statistically due to likely multicollinearity and sample limitations. These findings suggest tuning biochar properties for optimal microbial processing, taking into consideration environmental factors and using additional imaging techniques to better understand HAB- biochar interactions.

The many uses of biochar extend to microbial enhancement in fermentation processes because it acts as a catalyst and a support medium in agricultural industries, particularly for biofertilizer production. This study explores how three key biochar parameters, concentration (0.05–0.25% w/v), temperature (30–50 °C), and particle size (250 μm–1.40 mm) affect hyper-ammonia-producing bacteria (HAB) growth during fermentation using commercially sourced pine wood-derived biochar. Fermentation experiments utilized enriched cow rumen fluid under controlled conditions, monitoring bacterial growth via optical density (OD₆₀₀) over 48 h. Microbial proliferation was strongly influenced by all tested parameters (concentration, temperature, particle size). Highest growth occurred at 0.15% biochar concentration, 45 °C, and 250 μm particle size within the tested parameter ranges. Lower concentrations and smaller particles promoted microbial adhesion and colonization. Higher biochar levels hindered growth due to surface saturation and reduced pore accessibility. SEM imaging supported these findings by revealing structural changes on the biochar surface at different concentrations. Regression analysis demonstrated strong correlation between biochar parameters and microbial activity (R² = 0.9931), though multicollinearity limited individual variable significance. These findings support biochar optimization for enhanced microbial processing in biotechnological applications.

The production of microbial proteins (MPs) has emerged as a critical focus in biotechnology, driven by the need for sustainable and scalable alternatives to traditional protein sources. This study investigates the efficacy of two experimental setups in producing MPs using the nitrogen-fixing bacterium Klebsiella oxytoca M5A1. K. oxytoca M5A1, known for its facultative anaerobic growth and capability to fix atmospheric nitrogen, offers a promising avenue for environmentally friendly protein production. This research compares the performance of a simple bubble column (BC) bioreactor, which promotes efficient mixing and cross-membrane gas transfer, with static fermentation, a traditional method lacking agitation and aeration. The study involved the parallel cultivation of K. oxytoca M5A1 in both systems, with key parameters such as microbial growth, glucose utilization, protein concentration, and metabolite profiles monitored over a 48 h period. The results indicate that the BC bioreactor consistently outperformed static fermentation regarding the growth rate, protein yield, and glucose utilization efficiency. The BC exhibited a significant increase in protein production, reaching 299.90 µg/mL at 48 h, compared to 219.44 µg/mL in static fermentation. The organic acid profile reveals both synthesis and utilization regimes of varying patterns. These findings highlight the advantages of the BC bioreactor for MP production, particularly its ability to maintain aerobic conditions that support higher growth and yield.