Earth buildings are still a common type of residence for one-third of the world’s population. However, these buildings are not durable or resistant against earthquakes and floods, and this amplifies their potential harm to humans. Earthen construction without soil binders (e.g., cement) is known to result in poor strength and durability performance of earth buildings. Failure to use construction binders is related to the imbalance in binder prices in different countries. In particular, the price of cement in Africa, Middle East, and Southwest Asia countries is extremely high relative to the global trend of consumer goods and accounts for the limited usage of cement in those regions. Moreover, environmental concerns regarding cement usage have recently risen due to high CO2emissions. Meanwhile, biopolymers have been introduced as an alternative binder for soil strengthening. Previous studies and feasibility attempts in this area show that the mechanical properties (i.e., compressive strength) of biopolymer mixed soil blocks (i.e, both 1% xanthan gum and 1% gellan gum) satisfied the international criteria for binders used in earthen structures. Economic and market analyses have demonstrated that the biopolymer binder has high potential as a self-sufficient local construction binder for earth buildings where the usage of ordinary cement is restricted.

Modification of oil–brine–minerals interfacial properties with biosurfactant-producing microorganisms and their extracellular metabolites has been considered as one of the viable strategies for microbial enhanced oil recovery (MEOR). In this study, the effect of lipopeptide biosurfactant produced by Bacillus subtilis on the interfacial tension (IFT) and wettability in oil–brine–mineral systems was quantitatively examined by monitoring dodecane–brine IFT and the contact angle of a dodecane–brine–quartz system during cultivation of B. subtilis. The effect of high temperature (35–45 °C) and pressure (∼10 MPa), emulating conditions of in situ reservoir environments, on the effectiveness of the biosurfactant producers was also assessed using a custom-designed high-pressure bioreactor. Within the examined temperature range, it was confirmed that B. subtilis produced the lipopeptide biosurfactant (surfactin) with and without oxygen using nitrate (NO3 –) as the alternative electron acceptor. Thereby, the IFT was reduced from ∼50 to ∼10 mN/m and the wettability was modified from the values indicating an intermediate water-wet condition (θ = ∼45–50°) to a strong water-wet condition (θ = ∼20–25°). With the significantly improved capillary factor (γ cos θ) by a factor of 4.4, the two-phase flow simulations using the pore network model estimated significant increases in oil recovery rates in microbially treated reservoirs. The lowest rate and amount of surfactin production were observed at 45 °C, suggesting that higher temperatures may not be favorable for surfactin production by Bacillus spp. These results provide unique quantitative experimental evidence corroborating the feasibility of utilizing biosurfactant-producing microorganisms for MEOR practices targeting reservoirs with high pressure and moderately high temperature.

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Based on the processes occurring in natural Photocatalytic Systems of Pt Nanoparticles and Molecular Co Complexes for NADH Regeneration and Enzyme-coupled CO2 Conversion