Boundary condition in PDEPE function

Hi! I'm having some trouble implementing the boundary condition into the matlab PDEPE solver. The equations stand for bacterial density (B) and nutrient density (N):

dB/dt = D*d2B/dx2 - v*dB/dx + lambda*(N/(N+K))*B

dN/dt = D*d2N/dx2 - v*dN/dx - lambda*(N/(N+K))*B/Y

Shortly, the bacteria are seeded in a tube-shaped structure (in 1D, not in 3D). Then, an inflow of nutrients can enter from the left boundary. So the boundary condition are as follows:

At x=0 -------> flux(B)=0 and flux(N)=v*n_in

At x=L -------> flux(B)=0 and flux(N)=0

I'm quite sure that main script, equations and initial conditions are correct. My doubt is about the boundary conditions: is it correct the way I wrote them? I don't understand how to use the matlab equation p+q*f=0, although I've seen the examples on matlab's doc page and others forums.

This is my script:

% parameters

P.lambda=0.32; % [1/h]

P.K=0.1; % [mMoles]

P.Y=0.184; % [OD/mMoles]

P.n_in=2; % [mMoles]

P.v=1*(1e-4*3600); % [cm/h]

P.D=0.2*1e4*(1e-8*3600); % [cm2/h]

P.L=7; % [cm]

% time and space mesh

x=0:0.1:P.L;

t=0:0.1:100;

% pdepe solver

m=0;

eqn=@(x,t,u,dudx) sis_eqn(x,t,u,dudx,P);

ic=@(x) sis_ic(x,P);

bc=@(xl,ul,xr,ur,t) sis_bc(xl,ul,xr,ur,t,P);

sol=pdepe(m,eqn,ic,bc,x,t);

u1=sol(:,:,1);

u2=sol(:,:,2);

figure(1)

for i=1:5:length(t)

subplot 211, plot(x,u1(i,:),'-or')

axis([x(1) x(end) 0 5])

subplot 212, plot(x,u2(i,:),'-o')

axis([x(1) x(end) 0 P.v*P.n_in])

pause(0.2)

end

% function: equation

function [c,f,s]=sis_eqn(x,t,u,dudx,P)

c = [1;1];

f = [P.D;P.D].*dudx;

s = [-P.v*dudx(1)+P.lambda*(u(2)/(u(2)+P.K))*u(1) ; -P.v*dudx(2)-P.lambda*(u(2)/(u(2)+P.K))*u(1)/P.Y ];

end

% function: initial conditions

function u0=sis_ic(x,P)

u0=[0.01;0];

end

% function: boundary conditions

function [pl,ql,pr,qr]=sis_bc(xl,ul,xr,ur,t,P)

pl = [0;P.v*P.n_in];

ql = [-1;-1/P.D];

pr = [0;0];

qr = [-1;-1/P.D];

end