Answer
The electron lepton number is not conserved.
Work Step by Step
The proton $p$ has $L_e = 0$
The antiproton $\bar{p}$ has $L_e = 0$
The $\Lambda^0$ has $L_e = 0$
The $\Sigma^+$ has $L_e = 0$
The $e^-$ has $L_e = +1$
The left side of the proposed reaction has net $L_e = 0$ while the right side of the proposed reaction has net $L_e = +1$
Therefore, the electron lepton number is not conserved.
