Microbially-Induced-Calcite-Precipitation (MICP): A biotechnological approach to enhance the durability of concrete using Bacillus pasteurii and Bacillus sphaericus.

Developing bio-based self-healing concrete aims to minimize durability problems related to cracking. In this study, MICP was used as a smart and eco-friendly approach to produce bio-based durable materials. Bacillus pasteurii (BP) and Bacillus sphaericus (BS) were added into mortar mixtures with 0.25% and 0.5% cement weight. All treated samples exhibited a significant decline in water uptake, capillary permeability, and volume of permeable voids, as compared to control with no bacteria. All treated samples showed significant increase in compressive strength by 28-50%, after 28 days of curing. At the age of 120 days, the flexural strength of all treated samples was significantly increased by 19.29-65.94%. SEM imaging and EDAX confirmed that treated samples were denser with less voids due to MICP. DTA verified that the calcite amount and the crystallinity degree were improved in treated samples. Load deflection of bacterial Reinforced-Laminates had less deformation than control. Reloaded bacterial Reinforced-Laminates exhibited excellent restoration of physico-mechanical properties and performance, after 28, 90, and 120 days, confirming the healing process. Microbial self-healing is an innovative approach for continuous repair of micro-cracks in concrete, improving its durability, thus can reduce the maintenance costs.

Gastric outlet obstruction - looking for a syndrome: Bouveret or Mirizzi?

INTRODUCTION AND IMPORTANCE: Gastric outlet obstruction can result from any pathological process that causes intrinsic blockage or extrinsic pressure on the distal stomach and duodenum. Gallstone related gastric outlet obstruction is a well-known entity classically due to a cholecystoenteric fistula formation. CASE PRESENTATION: We present here a case of a 36-year-old man who presented with right upper quadrant abdominal pain associated with marked nausea and vomiting. Abdominal CT scan done in the emergency department revealed a large impacted infundibular gallstone with signs of acute cholecystitis, associated with prominent gastric distention. Gastric outlet obstruction was due to stenosis at the duodenal level from external compression by the large impacted stone with no evidence of fistula. Laparoscopic cholecystectomy was performed with total resolution of symptoms. CLINICAL DISCUSSION: Gastric outlet obstruction can be secondary to many etiologies, and notably gallstone disease. Classically this is due to formation of a cholecystoenteric fistula and intrinsic obstruction by the migrated stone. Our case is unique in that a large impacted infundibular gallstone caused gastric outlet obstruction with absence of any fistula or gallstone migration. CONCLUSION: Gastric outlet obstruction due to external compression by a non-migrated gallstone is a rare undescribed entity. Surgical treatment should not be delayed to prevent complications and fistula formation.

Production of bioconcrete with improved durability properties using Alkaliphilic Egyptian bacteria.

Microbial-based self-healing of concrete represents innovative technology for improving micro-crack sealing. Microbial bioactivity can induce calcite-precipitation in concrete, which seals micro-cracks. In this respect, two Egyptian bacterial isolates were selected and identified, as Bacillus subtilis (Bs) and Bacillus megaterium (Bm) using MALDI-TOF/MS-Biotyper®. Peak patterns of the bacterial ribosomal proteins showed a high match between samples and standards, which verified species consistency. Bs and Bm were added to the mortar mixture in two concentrations (0.5%, 1%) of cement weight, then the mechanical and physical properties were tested throughout a 180-day time course. The compressive strength of Bm0.5 bacterial mortar samples was increased by 21.4% after 28 days, as compared to control. The rate of water absorption of Bm samples was decreased by 12.4% after 180 days. Bacterial mortar samples showed significant restoration of compressive strength than the original samples by 44%, 21%, and 52.6% for Bs1, Bm0.5, and Bs0.5, respectively. SEM and EDAX analyses confirmed that bacterial samples were denser with fewer voids than the control, as a result of microbial nanosized calcite-precipitation. DTA verified that the amount of CaCO3 and its degree of crystallinity were increased in the bacterial mortar samples. Load-deflection of reinforced-laminates for bacterial mortar samples showed ductile behavior and less deformation as compared to control. In this work, novel concrete with improved mechanical and physical properties has been developed using selected Egyptian microorganisms, it can promote self-healing of micro-cracks with improved durability of the concrete. The application of self-healing bioconcrete can reduce the inspection and maintenance costs. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02781-0.