###### Abstract  
In recent years, traditional material for coastal erosion protection has become very expensive and not sustainable and eco-friendly for the long term. As an alternative countermeasure, this study focused on a sustainable biological ground improvement technique that can be utilized as an option for improving the mechanical and geotechnical engineering properties of soil by the microbially induced carbonate precipitation (MICP) technique considering native ureolytic bacteria. To protect coastal erosion, an innovative and sustainable strategy was proposed in this study by means of combing geotube and the MICP method. For a successful sand solidification, the urease activity, environmental factors, urease distribution, and calcite precipitation trend, among others, have been investigated using the isolated native strains. Our results revealed that urease activity of the identified strains denoted as G1 (_Microoccus_ sp. ), G2 (_Pseudoalteromonas_ sp. ), and G3 (_Virgibacillus_ sp.) relied on environment-specific parameters and, additionally, urease was not discharged in the culture solution but would discharge in and/or on the bacterial cell, and the fluid of the cells showed urease activity. Moreover, we successfully obtained solidified sand bearing UCS (Unconfined Compressive Strength) up to 1.8 MPa. We also proposed a novel sustainable approach for field implementation in a combination of geotube and MICP for coastal erosion protection that is cheaper, energy-saving, eco-friendly, and sustainable for Mediterranean countries, as well as for bio-mediated soil improvement. As an alternative method, earlier studies used the microbially induced carbonate precipitation (MICP) technique focusing on ureolytic bacteria within the field of geotechnology and civil engineering [3]. Among them, [PERSON] and [PERSON] conducted several studies in Ishikawa and Okinawa, Japan focusing on beachrock formation mechanism [4; 5]. They found significant information to protect against coastal erosion using the MICP method, which they called \"artificial beachrock\". Moreover, for coastal erosion protection, the attention of using hard and soft structures, such as geo-tube, beach drainage system, vegetation, sand fencing, artificial reefs, and green belts, are dominating with progressive knowledge [6]. Recently, geo-tube technology has converted from being a substitute construction technique to a key solution of choice in a more advanced way for preventing water logging conditions, as well as coastal erosion protection [7]. The traditional geotextile tube technology for coastal erosion protection is not sustainable because of the penetration of UV (Ultraviolet) rays that could accelerate to damage the geosynthetic product very easily; moreover, it is rather difficult to recover or repair, which would be considered as costly [8]. Therefore, this technology needs to be improved and, hence, we proposed a novel approach to protect coastal erosion through a combination of MICP and geotube, which is more eco-friendly, cost-effective, and more sustainable. There are various metabolic pathways leading to MICP, and urea hydrolysis is the most prominent for the formation of beachracks [8; 9]. The reactions occurring in this mechanism are represented by the following equations (Equations (1)-(3)), wherein urea hydrolysis occurs by urease enzyme and produces ammonium ion and carbamate, mentioned in Equation (1), and subsequently, the carbamate ion is hydrolyzed to form an additional ammonia ion and bi-carbonate, shown in Equation (2) [10; 11]. \[\mathrm{CO(NH_{2})}_{2}+\mathrm{H_{2}O}\xrightarrow{U^{\textit{U}ense}} \mathrm{H_{2}NCOO^{-}}+\mathrm{NH_{4}^{+}}, \tag{1}\]  
\[\mathrm{H_{2}NCOO^{-}}+\mathrm{H_{2}O}\ \xrightarrow{HCO_{3}^{-}}+\mathrm{NH_{3}}. \tag{2}\]  
Then, calcium carbonate is formed and finally precipitated, which plays a major role for binding the sand particles.